I know how you feel, Lut. When I was younger(I'm still young but I mean like 12-17) I had a high metabolism but the doctors experimented with the right medicine for my depression and my metabolism went downhill. I could eat huge meals and not gain a pound. I'd give ANYTHING to get my high metabolism back. If I didn't suffer from stupid depression, I'd still have my high metabolism. Sometimes life isn't fair.

Also,

exercising will help and having a good diet. (I need to have a good diet but I am addicted to junk food )