Does he possibly want me back? Or am I just a friend? Or a backup? or is he confusedHow can I tell?

He is a player. I think he is using you as his backup. If something does wrong with his girlfriend then at least he has you. You should just get over him because if you and him were never offical but after a week him and some other girl are thats just not right. That shows what kind of guy he is.