Okay. I've been in a similar situation.
My ex girlfriend asked me out in the cafeteria. She was really sweet about it, and so I said yes. We dated for 3 years before I broke up with her. But... After about a year and a half, I fell for my best friend at the time. I even kissed him while still dating her, and I felt so bad about it. (I did end up dating that guy, but for only two months.)
My advice is... break up with your current boyfriend. It's obviously not working out and like
>>2 said, it will only be worse and hurt more as it continues. Then wait. Don't get into ANY relationship again for a while. Give yourself time to be single and think. I regret only waiting a month before dating that guy. And realistically, I shouldn't have dated him at all. I rushed into things and messed a lot up. Don't do it. You'll regret it.
Give it a couple months. If you still have feelings for the other guy, go for it. And don't worry about what other people think. Hell, that guy might not even be the right guy for you. And that's okay. After the drama with my ex girlfriend and boyfriend, I finally have a boyfriend that it feels right to be with. When you find that person, you will know. Good luck, I hope this helps.