He did it for the sex, she was his conquest. Would I get into a relationship to conquer someone I hate but pretended to like or someone I just felt would improve my status or self-esteem?
then you are a cheating ass who should break up with her before looking for someone else?
its ok if its an open relationship and she knows about it, but if you are supposed to be exclusive and you have a girl on the side it makes you a dirtball.