Why should I keep trying?

Everything is falling apart. I can't even eat or sleep anymore. Everything hurts. I used to use sports to cope but no I'm injured and can't. I feel so fucking useless. My sister keeps saying shit to get under my skin and whenever I say something back I get in trouble- just because I'm older. I don't want to be in a place where I constantly feel invisible. I do my best work and that's not even praised. I've lost of friends trying to a keep a relationship only for that person to turn out to cheat on me. I just failed a quiz and my grades are decreasing like nothing. I'm ugly and have no looks to go off of. I've destroyed my body and gave it so many battles to fight, yet I don't even want to keep it fighting anymore. I remember nothing from when I was a kid except for the bad memories. I don't want to live where all I'm going to be is a burden to everyone.