Yes, the problem is that you don't eat. Your body needs food to function. With out the proper nutrients your organs will shut down, your skin will dry out, your body wont be able to fight off little things like colds (which is probably why your sick so often), your hair will fall out, you will lose the ability to have children, your nails and teeth become brittle, the list goes on. If you continue this behaviour I fear that death will be in your near future and I know that you have people that love you and they would never want some like this to happen to you. When you purge the esophagus, vocal chords, and stomach are damaged and your esophagus will eventually erode and your breath will smell and your teeth will rot. Besides, you only lose, at most, 50% of calories consumed and thats if you purge straight after a meal so it doesn't have much effect on your weight at all really.
When you say you ate heaps you really didn't eat enough. You should be eating 6 small meals a day. That is breakfast, lunch and dinner with snacks between each. Teens especially need to make sure they get enough nutrients because their bodies are growing and developing and without proper nutrients you wont develop. At your age you should be gaining weight rather then losing it.
This is a serious issue and I think it would be good if you talked to some one about it. Personally, I believe you should seek the help of a professional because you could be classified as some one with an eating disorder and with out professional help your future looks bleak. You should also consult some friends and your family about your problems. They will offer you much help and support through this and you will find they really make a difference in those difficult times.
If all else fails you can also make a topic here on livewire ti vent your feelings and if you ever need to talk to some one you can PM me any time you like. I hope I helped and I wish you good luck, you can do this.
~Dazi
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Think.
Do.
Be.
Positive.