Whats wrong with me? if anything...?

I can't form a proper relationship with people. I have had a girlfriend but we haven't ever connected mentally. I sit in the library lunch after lunch doing work; and find it hard to do anything when I need to. I know I have loads of things to do; essays, labs, IA's, IOP's - but I sit there in bed until 5pm and can't move. The biggest social connection I have is on games; and yet that's just giving advice to people on the game. I don't feel I have any true friends, or that anyone can truly understand what I am. I don't understand. I sit and jam my guitar whenever I am in a sombre mood; all I like to listen to is blues and jazz/guitar music. I don't meet peoples eyes when I talk to them and hear nothing but words from them. I can't understand the emotions people give off; and I don't care about them either. Whenever I have an up and try especially hard to work, My grades become 100's. When not, I get into trouble because my school is private with high standards. Although I am a teenager, I also have an incredibly sexual mind. I masturbate around 6 times every day, maybe more, and constantly want to have sex with my girlfriend when she's around me. Yet my mind wanders to other people; anyone and everyone, when im alone. Sometimes, when someone really annoys me and one of their views gets in the way of my reasoning; I want to kill them. I want people to physically die; and I never forgive most. I am abnormally strong for someone my age; from the age of about 7. When I was 12 I was beating people aged 16 in arm wrestles, but I never physically hurt anyone. I know I could, because I used to - while playing little games with my friends. When I was 15, I sort of jock came up to me and asked 'squeeze my hand as tight as you can' He was trying to prove a point, and I did. I broke his little finger. What is wrong with me? Do I have too much testosterone? Is there something genetically wrong with me?I feel at ease alone with my guitar or reading. Yet everything in life seems simple; its everyone else and their ridiculous moralities and emotions that make the world complicated.