I feel like he won't divorce as it's too comfortable now
No, he won't divorce his wife because he gets to **** two women regularly. So why mess that up.
It would cause so much upset.
Not nearly as much upset as it will cause when his wife finds out.
He has told me if he never had me there is no way he would have an affair with anyone else,
I would not bet on this being true.
it is so clear his wife doesn't care as much for him.
Do you know how many times the women who have posted on a2k about having affairs with a married man have said this? Every one of them. Your married guy is no different if he is telling you this. The fact is you have no real idea how much she may or may not care for him. You have no idea how well or how badly she treats him. You only have what he chooses to tell you and frankly, he is a proven liar so odds are he is lying to you. (He is most certainly lying to his wife about where he is when meeting up with you, thus he is a liar.)
I just always wonder why he didn't leave her
He didn't leave her and still will not leave her because he is happy with her. If you were anything more than a piece of ass on the side then he would leave her. People divorce all the time. He just does not want to do so.
Bottom line, you know having the affair with him is wrong but you want what you want and to hell will his wife who believes and trusts her husband is being faithful.
So I have two suggestions for you. If you are determined to keep screwing him, why don't you suggest to him that he talk to his wife to see if they can come to an arrangement where she can screw around also. Shouldn't she be given the same opportunity that he is having? Of course, that means he would be telling her about his affair with you, but if screwing you is such a good thing, why keep it a secret. And this way she can give her blessing and have some on the side also. Or decide that divorce would not be as devastating as being married to a cheating bastard. Either way, she gets a say in whether she stays or ends her marriage instead of letting it all up to him.
Or end things and find someone who is unattached. (Or just stay with your current boyfriend, but I'm guessing if you are willing to screw this other guy that things with your current guy are not working out so well.) I wonder what your current guy would think about your screwing around?