Either ask him why he didnt tell you and start a big thing with him about how it makes you uncomfortable and he should have told you and blah blah blah or let it go. I suggest letting it go. It's the past, not everyone deals with depression the same way, guys will have sex with girls who are way less attractive then them so looks arent everything and GROW THE F*CK UP.

Good luck.

"Don't fall for someone who's not willing to catch you"

Yikes. Eh. I can see why it bothered you that he didn't tell you about that past after a long time dating, BUT it's the PAST. LET IT GO.

Guys think with their dicks (sometimes, most of the time, depends on the guy...). So of course it probably felt more therapeutic for him than anything. And what's up with her not being so attractive as you? Oy. Guys will practically have sex w/ anyone attractive or not as long as the other person actually agrees to it.

Bring it up to him that you don't appreciate how he covered it up and then let go, if you can't let it go and you consider this as an act or 'betrayal,' well there's only one option: OUT.

*Unconditional love is a beautiful thing, just be sure to give it AFTER your conditions have been met.*

Yikes, I can see why this would be an awkward situation for you. I'd talk to your boyfriend and get some reassurance from him, but after he talks openly with you about the situation and does some reassuring, if you still can't let it go then I think you should let him go.

Have you told him about all of your past excursions? Well, maybe that's exactly the reason he didn't tell you. Some things are just better left in the past. Unless there's new evidence that he's still sleeping with her, then I would just do as the others suggest and mark it up as his past and let it go.

It sounds like your boyfriend was really honest with you (after he was pushed) about something he wasn't so proud of. it doesn't sound like they had sex because they were attracted to each other, more out of lonliness and depression. it sounds like a sad situation all around, you should be glad that now he is in a better place and chooses to stand with you.

I can understand why you feel like this, because you are her friend too, and neither your boyfriend nor she bothered to let you in on their past moments of lonliness and depression for at least 18 months! The proper thing to do is what the above said and let it go. You know about it now. If you feel like he lied/is lying to you, then it's time to end it if you can't get over it. Hard choices. Do you still trust him with or without her? At least you know the girl, and she's in another relationship, as well. It always seems to come back to this simple, yet often ignored basic thing; *trust your instincts*.
Good luck, stay strong.

I'm curious as to why it makes a difference that they were living together or not living together for why he didn't tell you? I don't know any couples that sit down and say I've slept with these people. Sure if someone asks I think it's fair to tell but in no way an obligation. But generally if that person is not an issue I don't see why someone wouldn't tell when asked. I don't hide anyone because none of them are an issue, I'm choosing to be with whomever it is I am dating. But I am not going to come out and be like you know I slept with her for a while or whatever the case may be. If your curious ask, get your answer and like all above have said let it go and move on. He's chosen to be with you and whatever his reasons were for being with her before you all got together are between them. Best of luck.

sorry but what's the big deal? people cope with issues different ways, and just because they found solace together shouldn't give reason for it to not sit right with you. also it doesn't sound like he was necessarily hiding it, but it could just be a person that he was with but never really thinks about, or that he wishes he never had that sexual relationship with and so he doesn't think about it, or just that he could even feel badly about why the sexual relationship started in the first place (since it was based on a mutual depression) that he doesn't want to go boasting that he was with her. It doesn't have any relevance in your relationship now and you really should just let it go.

It is true that couples don't need to go into detail and name every person that they have been involved with in the past. The part that doesn't sit well with me is the fact that this best friend is still a constant part of his life and hangs out with them, yet the girlfriend had no idea that this girl she was hanging out with and probably starting to build a relationship with has had sex, and often, with her boyfriend. I don't know about the rest of you, but I think sitting in my living room with a girl who has seen every bit of my boyfriend would feel a little weird. How many people here are friends with a girl who slept with your boyfriend?

Jeze, what you are saying makes a lot of sense. I have slept with several of my very close female friends. It's one of those we both want to know so we try it things. And I'm still close with all of them. Only one girlfriend has had a problem with it. It has always come down to how comfortable both people make them feel. I know a few girls I have dated have slept with some of their male friends or thought maybe they had but I never felt threatened because of it. Personally I think it has more to do with believing in yourself and in the relationship. But if you are uncomfortable you must speak up so that you can become comfortable.

I am totally with jezebella. This is not just the past! This girl is still a part of both of their lives and the gf just doesn't get to know what has really happened between them? If it was a girl the bf never talked to anymore, then yeah, that's the past and it should be left alone...but this girl is still a major part of their lives! That would be so awkward and weird to all of a sudden learn that this girl you were getting to know that you thought was just your bf's friend has slept with him multiple times! Thats crazy! I would just be so completely mad that the bf didn't tell me that!

Clarby: Yeah, it just matters how comfortable everyone is with the situation, I agree. So how exactly can the poster be comfortable with the situation if she doesn't even know whats going on b/c the bf didn't tell her? That's a choice (being comfortable/ok or not with the situation) that the poster should make for herself right, and she by default choose that it was ok.....B/C SHE HAD NO IDEA WHAT WAS GOING ON!

This is not in the past b/c the girl is still there! This is one of those times when the b/f SHOULD have gone into detail and named the girl he slept with B/C IT AFFECTS THE POSTER!!! I wouldn't be upset that he slept with the girl, b/c yes, that was in the past and doesn't matter...I would be upset that he didn't tell the poster. I prob. wouldn't trust the guy now b/c I would wonder which of his other friends he has slept with etc. etc. But I have trust problems b/c of jerks...so...thats just my opinion...

That's the thing about depression, it can definitely make you feel more sexual. I think it's also why some prescription medications have a tendency to put that fire out. Not that i think them doing it actually helped the depression but, he should've warned her. I mean, that chick's girlfriend knew and i don't believe it was by accident. The OP should've been told.

I'm all for people being honest at all times, its the only way a relationship can really work. Dear Sugar posted on cheating the other day and I believe one should tell no matter the circumstance. However this is pre-relationship. While the person is still a part of their life, she is not a sexual part of his life anymore. I don't think he was trying to hide the fact. It's not something you just come out and say to someone. FYI, Suzy BFF and I slept together, there is nothing to worry about. It'd be one thing if they flirt a lot and tease each other and made her feel uncomfortable but it doesn't sound like that is the case. It sounds like she found out they slept together and it bothers her. I'm not understanding why? And if a guy needs to tell a girl he starts dating which of his female friends he has slept with, how does he go about doing that and when does he do that? I think this is an if asked be honest but if not asked it really shouldn't matter if a person has confidence in the relationship.

Hm, honestly, I don't see what the big deal is. Many guys are close friends with their exs, and your boyfriend and her didn't even have anything serious. Is it because he didn't tell you? Well, it's in the past! It sounds like he doesn't consider the sexual relationship he had with her important at all, and maybe even regrets it since they were both at bad periods in their lives. Just let it go, it has no relevance in their present friendship, and neither in your relationship with your boyfriend.

Eh. Um.

My fiancee's ex (his ex-fiancee) is also my bff (well, my fiancee introduced us--he was roomies with her and her bf, he thought I'd love her, and I do). We're like sisters, we have similar mindset and attitude. We hang out together, have fun, and yea, I don't get jealous of her, vice versa.

We actually have gossiped about my fiancee about his 'ability' in bed and such. We've actually made fun of his 'antics' from time to time. I know most will think it weird, but hey, it's working just fine for moi.

Most of the time I don't care about people's past..BUT only 1 rule for me: Just be upfront about it then I know what I'm dealing with. So in that part, I kind of get what OP's feeling.

But yess, OP, you seem to be insecure anyway, that's why maybe they'd rather not let u know. Hmm.
If you wanna stay, you gotta deal with it, if you can't deal with it, you'd rather leave, that's no easy way out.