I've been talking to this guy for about a week now, and we're really starting to kick it off. I can tell he's definitely interested, and we've hung out a couple times in group settings. I feel like I already have a major crush on him, but what's holding me back is that he hasn't been single for that long. I know his ex, too — she's supernice, and I don't know what caused the breakup. Mutual friends are saying it's cool and I should go for it, but they dated for two or three years and broke up five months ago. I'm scared to start anything in case he still has feelings for his ex. Opinions?