boyfriend never cum

My boyfriend was a virgin when we first had sex. He never actually cums, and I don't think he ever has. He doesn't reach orgasim or ejaculates. When he gets pre-cum he thinks that he has ejaculated. I have to tell him that that is not what actual ejaculation looks like. He takes alot of phsychiatric medicine and is some what mentally disabled. I'm beginning to wonder if he is developmentally disabled as well. Alot of times he seems slow and I'm not sure if it's the medication causing it. He seems so smart in other ways like he is extremly political and knows things that even I don't know. He even knows three languages. But when it comes to dealing with people and every day life situations he is somewhat like a child. He has lived with his parents his whole life, he's 29 and doesn't know how to support himself. He doesn't know how to deal with people. So one day I asked him if he had ever been diagnosed as slow and he said yes. A few doctors had diagnosed him as developmentally disabled. He has been diagnosed so many different things at different times that it's hard to tell. Shitzoid effective is one and I have learned that shizoid effective disorder can make a person seem slow when they are actually very smart. With him it's hard to tell because most people that are developmentally disabled are pretty obvious and he's not. I guess there's different levels or different kinds and when mental illness is mixed in it gets confusing. I don't care what he is, I love him no matter what. Some people like to make fun of him and target him but I figured it was just because he dresses excentrically. I didn't really know that he had all these problems when I was first attracted to him. Maybe if I would of known that he was developmentally disabled I would of backed off although it wouldn't have changed the fact that I was attracted to him. What threw me off was all the intellectual stuff he liked talking about. I thought he was highly intellegent. After a few monthes into the relationship I realized that the stuff he liked talking about was tied in more with dellusion and often repeated. Also he's pushy about his topics and he gets mad if I don't always want to get into intellectual conversation with him. I can't because he talks non stop all day. I knew he was taking medicine but I didn't know that his diagnosis was deeper that I thought. He is liking sex more and more though. He's even getting demanding about it. He used to have to take viagra but now he sometimes doesn't have too. Yet, he still doesn't reach orgasim. What is the reason why and what can we do about it? He also has violent tendencys and I have wittnessed him hitting people. He once threw money at a cab driviers face. I worry about him. He made someone so mad once that the person he offended tried to hit him with a car. He can be a real as****e sometimes. His anger is misguided and confused. The people that he gets angry with have no idea what they've done wrong. So you see, he doesn't always seem so innocent although he is. In the past when him and I had had some simple arguments that every couple has had, he got irrational, scared, and called the police because he didn't understand what was happening or he would go to his parents house and tell them every thing! The police never did anything. They just told me that he's sick and to make sure he takes his medicine. So now I am very careful of his feelings. He has however never laid a hand on me. He's on SSI so there's a clear indication that he's disabled. All he has is his parents and me. He likes to take me out, take charge, he wants to spend money on me and on fancy dinners but I know that he can't go too far seeing that he's on SSI. I want him to feel like a man so I let him take charge of our dates but I keep an eye on him and his spending. He's actually pretty good at finances and is very maticulouse and organized so there's no problem there. What kind of illness does this sound like? How can we improve our sex, and how can I take better care of him without immasculating him?