Your situation sound a lot like one of my friends. This is definately not a health relationship for either of you. A basis of every relationship is trust. There is some serious trust issues on his part. He is obsessed with you and cannot trust you with anyone else but himself. He really needs to see someone, like a professional, for help. If he really loves you and cares about you, then he will do this. Otherwise, you might have to break up with him. I know then he will definately cut his wrist more and really make your life miserable. Before doing anything like that, I think that you need to talk to someone in his family like his parents or siblings or something so that they can help him too.