Crazy as this sounds, everyone knew who I was, I had tons of friends, whether I wanted them or not. I may have moved from school to school and met many people but wanted to stagnate and stay in one place and have a few friends. All I wanted was to be left alone, but unfortunately (fortunately, I don't know) it didn't take long for people to flock to me. I know this sounds like I am pumping myself up, I am not, this truly happened to me. All I wanted was what my sister had (to not have many friends but have a few close friends that I could keep in touch with).
My anxieties have always been being in crowds, strange people, strange surroundings, strange sights etc.
With depression as a teen, it didn't matter how many friends I had, I knew that I would be leaving soon and I couldn't very well tell any of them my problems just to move a couple of months later and be cut off again, so it was easier just to not say anything and not to get too close to anyone.
My suggeestion to teens now would be talk to someone, anyone and get the help you need now before you start cutting, or anything else to self-harm. If you survive, you will have scars which are difficult to explain to people. Talk to the school counsellor, talk to a fellow student, talk to a social worker, talk to a friends parent, talk to a teacher, find a website like this one, just talk to someone. Nowadays, there is alot more help out there than when I was young (kids help phone didn't exist, internet was something you hauled out when you went fishing with your uncle, and mental illness was hush hush).