This is a no-win situation. It's easy for him to tell you everything emotionally that you want to hear because he doesn't have to back it up. Maybe there's a greater sense of need and excitement between you two because you both want what you can't have. You need to step back and look at this for what it is. This is a guy, living with his girlfriend who has stated to you that he has NO INTENTION of leaving her. Why are you setting yourself for future hurt like this? Pick up your self-esteem and find someone who's going to give himself to you wholeheartedly.

And you know, you said that you've been cheated on before so you know how it feels which is why it boggles my mind why you would choose to put someone else through that. I wish women would be more empathetic to each other and not let a man come between what the right thing to do is, even if it means that you have to be the bigger person and walk away.