Worried about my son's mental health?

My son is 17, almost 18 and a senior in high school. He is very antisocial and detached from everyone around him. He has one friend, who he has had since he was very young but has never had any others and out right refuses to socialize or interact with his peers. Never had a girlfriend (or any romantic interest) for that matter, and seems to just push everyone away by a either a complete lack of social skills or just being rude to make them go away. I've talked to him many times about this and the answer always seems to be the same. He says he doesn't see any rational point in socializing or making human connection and that its all very platonic and illogical. That being social is a weakness because it creates a need that is unecessary to survive. He is extremely smart and can build, fix, or solve any problem that comes at hand. Literally he can fix any problem with a car, computer, most advanced math problems, he is incredibly gifted at art and sciences, and is even very physically fit, but lacks desire for anything els. Work ethic is great and that's all he does is work, research, read, and spend his time alone or helping someone with something. He just plainly does not like being around people, and hates being touched, as in he will pull away as if being burned if I or anyone else attempts to touch him. Hates school even though he does the work with out even trying. He finds school very trivial and has missed about fourty days per year of high school because he doesnt see the point in attending, just enough to get his diploma. (I have adopted him), but he seems to have taught himself everything he knows. Cold, calculating, ytical, but at the same time he seems to help people in very quiet ways and hopes no one notices so he wont have to endure getting the credit and attention. I'm worried that he is unhappy even though he continuously says he is very content with his life when I ask him. He was horribly abused physically, mentally, and ually as a child, and has lost a lot through out his life mostly to the few he loved killing themselves and other violent episodes he has had to endure when he lived in poverty. Could these all be symptoms of a mental illness, and what kind of physcologist should i take him to?