Worried about my son's mental health?

I adopted my son when he was eleven, and has always been a socially isolated child. He is now 17 and will be 18 in July, a senior in high school. When he was a child his biological mother was using and went through many boyfriends and several extremely abusive husbands. He was beaten severely on a daily basis for most of his childhood and was forced to watch his biological mother be sexually abused nearly every night. On top of that he grew up in poverty and the closest person to him (his older brother) killed himself in front of my son when he was 14. That mixed with all the violence and bloodshed he saw living in the projects worries me. I was informed by adoption agency psychologists that despite all this he was emotionally stable and did not suffer from any mental illnesses or severe depression. However, like i said, he has always been socially isolated. To the point where he doesn't have any friends and out right refuses to interact with his peers. When he was young and i tried to push him to play with other school kids he just shyed away or found away out of it. The thing is, he is incredibly intelligent. The most intelligent human being I've ever known. He is the most logical and calm person and can solve just about any problem. His critical thinking and ability to connect things and see patterns others don't amazes me. All he ever does is work, read, research, and understand things by himself. He is very independent and hardly ever asks for help with anything. Literally he can fix anything wrong with a car, computer, he can run through calculus, statistics, physics, chemistry courses like they are nothing to him, and at he same time he is also artistic. Not to mention he already knows three languages. Also, he's not a "nerd" either, in fact he is athletic and physically capable and fit. But he hates people, especially loud environments and gets very upset when he is forced into a social engagement. He only has one friend, a girl who he has known for the majority of his life, but never had a girlfriend or any romantic interest for that matter. If she comes over to the house he gets very very nervous to the point of shaking and being nautious, he won't say why. I don't think he lacks social skills because he can "act" as he calls it and be polite and curtious, but he won't ever do that unless he sees something in it for himself. Most of the time he pushes people away by being sarcastic and demeaning to them. He seems to be to logical and analytical, he even tries to rationalize relationships. When i ask him why he doesn't want friends he always says something like he doesn't see any reason to have social contacts or play along with human platonic rituals. That interacting with others only creates an unnecessary weakness of dependence on other human beings, and he has no desire for human connections. He is just so detached from emotion and will stare at things and talk to himself for hours sometimes. Despite his emotionless surface he would never admit it but he is always helping other people with out them realizing it. He does this in such a quiet way, so not to get attention or credit because he hates that. On top of this he doesn't do things he deems "necessary". Like attending school on a daily basis. Every year of high school his has missed about forty days because he finds school trivial and hates it. Despite this he still maintains excellent grades which is honestly just to humor me. Appearing to be asexual, and complete lack of desire to be around other people, should i be worried? He wont even let me touch him, pulling away as if he has been burned if anyone attempts to touch him. I've considered taking him to another psychologist but i don't know. He just appears to always be miserable and it seems like working is his addiction for dealing with his misery.