Slimming out?

You should go to the doctors or a nutritionist to have them check your health and diet. Maybe you're under a lot of stress, poor eating habits or maybe you have a tape worm.

Abnormal weight loss when you're not exercising and increasing your metabolism is un-common I think.

Have you told your parents?

Hope you get better.

It could be something simple like losing fat and gaining muscle, that happens to me all the time when I start "losing", I lose belt sizes but no weight because muscle weighs more than fat.

Unfortunately rapid/unexplained weight loss can also be a symptom of some really serious illnesses (like cancer). You need to see a doctor ASAP to rule out anything dangerous.