How do I stop stressing so much?!

I'm in 10th grade in high school and I don't think I should be stressing this much. Everybody is worried about me, but I've been stressed this passed week because I had a ton of work, and it's also family problems, like my moms car getting repossessed, which means she didn't pay her bill and some people took it. She's paying the bill now though. I'm kind of starting to worry about myself too. I'm just afraid I'm going to fail all my classes. I don't know what to do, I'm trying not to stress so much, but I can't help it.