No easy answers. Here's a few thoughts on where to start.

1. This sounds like a medical issue. I encourage you to find someone to talk to. Either a mentor you trust or a certified counselor. Get a medical check up. This could be physical.

2. Invest some time in a physical activity away from school. Run, bike, hike, yardwork, walk.

3. Find a place to do some volunteer work.

No matter what, get some help.