So I am really needing some advice from guys. Ny boyfriend and I have been together 3 years and lived together for two. I found out we were going to get engaged next month, so its very serious. My boyfriend was cheated on by his ex fiancee about 5 years ago and after that he started visiting craigslist personal ads. I found out about it by chance about a month ago. He has been talking to men and women. I have no proof that he has actually physically cheated, but I do know that once about a year ago he got a text from someone (I was sitting next to him playing a game on his phone when it came) that said 'I want to f***' He text her back immediately and said that he was in a relationship and to leave him alone. I realize I should have been more suspicious then, but our relationship was so great and we spend 24/7 together I believed him that it was just some crazy random person he may have used to know. For our entire relationship he has been going on Craigslist regularly and posting/responding to ads, asking for pics, asking people what hotel they are at, etc. He says that he always did it as a self esteem thing, that it was just a taboo deal but he never actually cheated on me. I could believe that, if it wasn't for that text, because no one that you aren't sleeping with is going to say that to you at 9am, in my opinion. It's a pretty bold statement coming from anyone. He says that he loves me and he is sorry and will never do it again. He says that if I hadn't caught him he probably would have done it forever (even if we got married and had kids) so he is glad I did because now it feels like real life to him and he can see how much he has hurt me. Even writing this I feel like a moron because it sounds like a load of bull, but I love him and am struggling with what to do. He is my best friend, we do everything together, and we never fight (minor arguments are all we have, but we communicate really well and always solve things quite easily) and I just don't understand why or how he could do this if he was really planning on moving forward with this relationship and was so happy. I only found out about the engagement thing at the same time as all this, and they are such stark contrasts from one another. One moment he emails a girl telling him he will give her a ride in his car from her house to a nearby city and he is going to pound her and asks for pics and tells her he is drug & disease free and a safe, sane guy, and literally five minutes later he is telling someone else how much he loves me and plans to propose and his plans yada yada. Can someone please give me insight into a guys head?!?!?! Should I dump him and assume he is a serial cheater or give him a chance?