I feel so fat , please help:(?

I'm sixteen and I weigh 57 kgs :( (125lbs) and I'm 1.62m (5'3) . I feel fat because I gained weight, I used to weigh less but I gained 4 kilos (That's 8 pounds) since September. I feel so obese and yet I can't give up chocolate :( BUT I DONT WANT TO BE FAT :( Can you tell me how to eat less? I have almost no time for exercise these days...