Hiya,
you really are having a hard time aren't you? I really sympathise with you, as I went through a very similar situation 10 years ago myself. Being a teenager is really not easy these days. There are so many pressures on you from all sides: teachers expect you to get good grades, so do your parents, who also expect you to carry on with your education and stay out of trouble. Then there's peer-pressure, expecting you to do everything your mates do and be just like them. Being between age 14 - 21 is a very difficult and confusing time anyway, as you are learning to deal with your emotions, and become grown-up at the same time.
I would be surprised if your mates aren't going through similar emotions. But they don't sound particularly helpful, so maybe you shouldn't spend all your time with them. Are there any youth centres near you, that you could join? One of the leaders is bound to be trained to speak to you alone about your concerns, and may be able to give you further advice. You could also meet other people there your own age. It's not easy at your age not having a best friend to share things with, I know from my own experience.
Also, you could see your gp confidentially (if you are over 16, if you are under 16, I'm not sure what the rules are; they may let your parents know), who could put you in touch with a counsellor at the surgery. The gp may also be able to help you get back on track with your parents. Your parents, maybe particularly your Mum, is a very important person in your life right now, she knows you best, and will be able to help you best, if she really cares about you. Trust me, I am now a mother myself.
You could also try ringing the samaritans, confidentially, which you may think is just for 'crazy' people, but they get all sorts of calls every day, believe me. They will listen to you properly, and give you appropriate advice.
Last but not least, it may feel like you're in this situation for ages, but things will improve eventually. If they did for me, they will for you too. You'll get your own place when you're ready, hopefully meet someone nice, and start to feel properly grown up. But first just concentrate on finishing school, then decide in little steps what it is you would like to do next, education or work-wise, and also try different places out to meet new friends.
Best of luck, and best wishes, Katt.

hi,
it sounds as though you are putting yourself through a lot. have you tried speaking to anyone other than your friends? do your friends ever talk to you about their worries? it is likely that they are going through confusing and difficult things aswell. i know it sounds like a big deal, but your school may have someone you could go to for advice that would be totally confidential, and staffed by trained proffessionals. please don't think of yourself as selfish - everone has worries and anxieties but everone deals with them in different ways.