I was with a N for close to three years. First they start of so loving and attentive. They make you feel like you are their everything. Then they turn on a dime. I will say they are very good liars. What they say about you is what they tend to feel about themselves. I was told I was "needy" yet he is 31 and cant live without someone supporting him. Mine was abusive as well. I would catch him on chats with other girls and it would turn into a huge argument, one of which I ended up physically hurt.
He would tell me I don't turn him on and that he is not into sex and deny me months at a time. Yet I would catch him on meetme.com which is basically a hook up site. I would avoid an N if you can. It will only hurt you in the end. I did hours and hours of research on them and tried to convince myself that I could change him, he was different than the others.
The reason some of us believe this is because they can throw on the tears when necessary. They will act like they are good people but step back and observe. Mine would say how much he loved his parents and yet he would bleed them for every dime they had. He went to jail for being violent with his mother. When we are the person in the circle we don't see it from the third party perspective. The most intelligent of us can make some really stupid choices. When we love someone we have rose colored glasses. From day one my friends didn't like him. In fact most people didn't. I would say "he is so selfless" and they would say "really? that's not my perspective." I would say if you have not grown feelings of love for this person and you believe them to be an N. Run!