Romantic problem. HELP.?

i couldnt find any reason why he would allow you to break up, but that he just changed. maybe, someone/something must have influenced him to be that type of guy who would go out with that type of girl. or maybe, you just don't know him that well. at first, i really thought he was just doing that to make you jealous. but now that i have further read he did cheat on you during your relationship is just making him the wrong guy. hey, you deserve better than that.