Maybe he needs only a friend? If he have a girlfriend and he's doing something like this (he's playing on your emotions) such man isn't a friend ... He's just bastard! And even he doesn't do it deliberately, are you sure that the man that betrays his girlfriend, is a good material for a boyfriend? Of course it's your decision, I can't tell you what to do :) but in any decision you make, I will support you! :D And I'm sure that you won't regret it anyway :3