My boyfriend admitted that he had with his mother?

I knew long before I began dating my boyfriend that he had emotional issues. For example, when I first met him a few years back, he couldn't even look somebody in the face (he just stared at the floor). At first, I just thought him shy but after I met his family, it was clear why he was the way he was. His mother is not very stable (she goes from relationship from relationship and drinks and leaves him and his siblings basically babysit her and take care of her issues). We got into a huge fight over his mother being so overbearing (having the nerve to call me a sl*t when she's having an affair with her married boss) and we didn't speak for a while. Finally, we sat down and talked and he told me that from age eleven to fourteen, he had a ual relationship with his mother on and off (and it was only a handful of times and only happened after she broke up with whoever). He said he hasn't done it in three years. The way he spoke, it's clear that his mother has him convinced that he's in the wrong for "seducing her." He's very self-hating. I think is gross but I really feel for him. I mean, the way she acts around him, it does all fit (I thought he was just a mama's boy but now thinking about it, the way she acts around him is a little too ual for a mother/son relationship). Like I said, I feel bad for him but I don't know if I can accept it. How can I cope with this because I'd like to stay with him because he's just so nice. He's 17 (18 next month) and I'm 16.