Why am I obsessed with my looks?

I'm 16 years old and obsessed with how I look. I guess its normal for teenage girls to be so concerned with their appearance but I feel insecure that I don't look good. People tell me i'm gorgeous and beautiful ALL the time but I do not feel it. Is this normal? I wear makeup on my eyes, my hair is long and brown, and i dress sexy/stylish. How do I make myself feel beautiful. Im also obsessed with my body and staying fit. Im 5'5 125 pounds size 3 and my boobs are a full C, is that a normal body type? Do I need to lose or gain weight? How can I gain confidence or look better.