Hiya pink.
I felt the same way as you did at 15. I was a bit of a rebel, but not a troublemaker. I couldn't settle into any of my old hobbies, always thought my friends were having a better time than me and couldn't wait to leave home. I was very lucky that I had understanding and supportive parents. they didn't once hassle me to do what they wanted me to do, they advised, gave me options, let me make some mistakes along the way, but were (and still are) there for me. I made a major c*ck-up of some things at 16, like my A levels, started to think I'd be working in Tesco for the rest of my life and went to stay with my cousin for a while. He seemed so successful to me at that age, he had his own flat (rented) a regular job (at the time I thought he earned loads of money!) and a car. It wasn't until he got a bit drunk one night and showed me all the bills, his wage slips and talked to me about life in the real world, how he wished he'd tried harder at school, and shocked me by admitting my mum and dad had supplemented my keep so he could feed me that I sat up and took a bit of notice.
I re-sat and passed my A's getting (just about) good enough grades to get into uni.
Since then I've been really lucky, it's not been easy, I'm still paying back my student loans, but have a real career, a steady, loving, supportive partner and am now more settled.
Sorry if I sound like an old f_art. I'm only 24, but have seen a lot of life in the 9 years between age 15 and now. Keep focused and you'll soon find the world is a big place with loads of exciting experiences. My best advice is to enjoy your teenage years, coz they go past so very quickly.
Best wishes
Sam x