Teenager asks: "What's wrong with me? I eat a lot and I'm always hungry, even five minutes after a meal. And I'm losing weight. I drink a lot of water too. I know something's wrong."
Have you told your parents what you've shared here? You need their help and support to discover what is going on so you can get proper care.
For example, if you were anorexic you might believe you were eating a great deal yet actually be eating very little. So you would always be hungry and be losing weight. But if you had a tape worm you might be taking in a large number of calories without your body getting the nourishment you need. You would be starving while you were eating ample food.