I had some close friends for about 9 years. They grew into people I hated. I stopped spending any time around them and hung out with other people.
Maybe you should try making some new friends who are completely different? If you think they are air-heads, self-aggrandizing, idiots, well, it doesn't matter a lick about how judgemental or not you are being; you have every right to pick and choose those you spend time with. Do these people make you happy, make you feel good? If the answer is no...why are you their friend?
Having fun at somebody elses expense is a big no-no for me (Ironic, isn't it?). I don't tolerate it very well, I don't find that sort of humour funny...
As for people being overly critical; don't worry about it. Everyone makes mistakes. A heck of a lot of people probably make far more mistakes then you do. Try telling your teachers that. If you do this voluntarily and it is upsetting you, offer to quit and give them the option of finding somebody better. Chances are with a couple weeks without you, they'll realize how valuable your help truly is. And your help is valuable; don't ever think otherwise. If your help was useless, why would they let you do it?
As for the teacher who made a comment about your friends bottom; tell your friend you heard it. Tell your friend it is really bothering you. If your friend is really bothered as well, the best thing to do is talk to somebody about it. Don't accuse him of being a pedophile, just go to the administration and say "I heard the teacher say XXX about my friends bum , and that disgusts me. Perhaps I misheard, but it is bothering me." - Chances are, the administration (Priniple, Vice Principle) will be equally bothered.
As for the cutting - that is bad. I get the feeling you don't want to do it. I know far too many people who have cut and it never truly helped them. I don't think I am good enough to convince you not to cut here and now. I am not going to tell you it is dangerous, that you shouldn't do it; you probably know this already. But if you decide to anyways, please sterylize your cuts...I had a friend who got very sick and infected and had to be hospitalized.
You shouldn't feel like a complete reject; there are likely some really great characteristics and attributes special to you; I can recognize one just from your post; you are annoyed at your friends for having fun at others expense. There are certainly people that care about you, and I am certain there are things you are good at. You just have to find them, figure them out. Then do them.
What are your grandma and aunt doing that annoys you so much? Tell them it bothers you, and ask them to stop...chances are, they will.
If you are worried about your sanity, go to see a psychologist or psychiatrist if you can. They will be able to help.
I am a 17 year old male practitioner of BDSMLNOPQRSTUV...
LeVay Satanism composes approximately 60% of my religious beliefs. I agree with approximately 60% of LeVay Satanism.
I am a sadist (60%) I am a masochist (40%)
I am bisexual, or bipermissive. (75% heterosexual, 25% homosexual).
I seek no conflict outside my bedroom walls.