Ok... so my boyfriend use to hook up and do the whole friends with benefits thing. There is this girl he use to hook up with while we were doing just that (they are actually good friends). I also actually gotten to know this girl and she is not that bad and we've hung out a couple of times. Now my boyfriend and I have been together for a good 9 nine months we are doing pretty good. The girl is now gettig married and having a baby... my boyfriend thinks it's a mistake and I also "snooped" through his computer and found an email from him to her saying that he wants to talk meet up and talk with her. What could he say to her that he can't say to me you know. I just think that there could be some unresolved feelings for this girl.

There most likely is unresolved feelings. He bounced from her to you pretty quickly. The fact that he was hooking up with this girl while you two were should have raised a red flag. Looks like you learnt your lesson.