I'm really depressed and been for a long time?

When I was a freshmen I had super high self esteem and made lots of friends and chilled all the time and everything was good. Sophmore year I transferred to another school and made some friends. Then second semester I never really went out afterschool anywhere and just straight home until it became a riuting and never got invited anywhere and since I don't live close to any of my cousins or relatives I really have no choice. Now this year junior year the new friends that I made moved to another school because they basically got kicked out for low grades and Now i hang ouT with a not really close friend and some freshmen who act like little kids and I'm embarresed to have no choice but to hang out with them. Lunch is very boring and I wanna go back to my old school.I don't do nothing afterschool or weekends at all just play guitar or xbox. I've also created a social anxiety problem and don't feel normal and awkward. The way I'm writing this actually doesn't seem that bad but I can't express how super depressed and in pain I am. I'm alone, never had a gf, only child, no close friends, no life, I struggle to even smile or pretend I'm happy. Ive lost contact with my cousins when I was about 8 yrs old so they all probably hav a life or busy. Plus their far away. I'm alone just with my little brother and parents and my grandma. I think i samba Choke myself or drown myself. I'm screaming with pain in my head right now!!!!!!