Sex, love, no love, and the other.......

You need to force him to decide, if you want him to make up his mind, then you have to give him an ultimatum, break up with her, or I break it off with you. Until you do that he probably will continue cheating on her with you. As hard as it may be for you, you are the one who is enabling him to keep it up, stop seeing him until he makes up his mind!

I think you really have to assess your own feelings for said guy before you try to make him give up his girlfriend. Also, because he is cheating on his girlfriend you should also ask yourself if he might be lying to you about his feelings for you and if he might cheat on you if you ever made your relationship official. A relationship entirely based on sex (no matter how good it is) is not very stable and can be destructive, especially since there is an innocent bystander (his girlfriend) who could be very hurt by this.

If you know it's wrong then stop doing it it's never too late. The only reason he says things like that to you is because he knows you would fall for it. He's a player and all he wants is sex. If he wanted to be with you THAT BAD he would have left his girlfriend long ago. Plus all you have is great sex and that's not gonna make a relationship work. Leave him alone.