So I met this guy and we exchanged numbers but nothing really happened.. 6 months later i see him again as he is my flat mates friend and he came around to our house, only now he has a girlfriend. He texted me a few times and I was blunt because I new he was in a relationship.. eventually one thing led to another and he started seeing me occasionally, and then it became more and more frequent. He told me he was going to break up with his girlfriend which is why i could justify seeing him a tiny bit even though i new it was so so wrong and that i must be a bad person.. after a few months of this i told him it was either me or her and i stopped talking to him for a while but eventually i gave in and we started talking again. He has now broken up with her and she's moved to another city. He told me he wants to be with me but i don't know if it's possible for things to work, I would be crushed if he cheated on me and have told him this. He says he will do anything to gain my trust and prove himself, and i really care about him but I'm scared of getting hurt. Everyone always says 'once a cheater always a cheater' and that he could do exactly the same thing to me. Is there no hope for a relationship at all?