I'm 16 years old, girl. I feel exactly the same way. I have big dark circles under my eyes, and I hate it. I always look so tired, even when I'm super hyper. My teeth are crooked, but I can't get braces yet. I'm also insecure about my skin tone, I've had complete strangers tell me that I look sickly and yellow. I get so many pimples, on my forehead especially. I also hate my fingers, cause I always subconsciously pick at the skin around my nails when I'm stressed. I do karate and sometimes they'll take pictures of the whole class and post it on Facebook, I hate it but they don't let anyone skip the photo. I always see the pictures after they post it and I'm always the ugliest one. Sometimes I wish my parents would let me wear makeup.
I try to keep in mind that everyone has insecurities and that half the time no one sees your insecurities as anything but pretty. I also try to remember that God made everyone perfect. I started telling myself, "Perfect doesn't mean beautiful".