I am shy and have no friends please help?

I really don't feel comfortable talking to people because usually they want to end up play fighting with me (which I am very sensitive about these kind of things) or patronizes me for what I say. Also I am in high school-17 and over 6 feet tall but my voice seems to be not maturing when the rest of my body is. My voice still sounds like a ten year old, with lisps and it sounds like whenever I say "like" I say "wike" or if I say real, "weal". And I am pretty ugly, with a big head, alot of peole tease me about that. Whenever somebody tries to talk to me or "be my friend" they turn on me behind my back and tease me, when I dont do anything and keep to myself. When I try to start a conversation with somebody, he/she ignores me like im stupid or "teacher! help me this is a rapist from the pen!" kind of look on their face. Also many "gangster" people want to beat me up even for accidently bumping into them in the hallways at school (hallways are very crowded when there are 3000 people and 75% of them stand in the way of everybody), and I apologize, etc, but still. When I was younger, I had loads of friends and was popular, from "nerds" to "jocks", from kindergarten-6th grade. What happened? Why have people betrayed me and turned their back on me when I haven't done anything to them?