Wow! I think this guy has a serious lack of respect! For you and himself, including the other girl. If he has cheated with her,then I'm willing to bet that he has cheated with others. It is funny that when we have issues that some of us find someplace(like this) to vent and get advice.
So heres my advice, dump this guy and come find me!
I live close by to you! just kidding girl. But remember you are not alone.