"Insecurity will always rent the space it occupies, but confidence will own the building and any other room it steps in"
Instead of bashing your body, why not try appreciating it? Look at what makes you unique and embrace those qualities instead of trying to hide them. I have a cleft chin and all through out my life I have been teased for having what kids and even some students that I have taught refer to as a "butt chin". Looking in the mirror, I saw nothing wrong with my indentation, because of something my daddy told me when I was younger. He told me, "Amber, that's considered an angel's kiss, not many people have that, it's what makes you, you". And he's right, I wouldn't be Amber if I didn't have my cleft chin, it's just part of who I am. Instead of hating or trying to change what makes you, you, embrace it.
You don't have to love every ounce of yourself all the time, but work towards celebrating the positive instead of harping on the negative. Being insecure is only a waste of time and takes away from your self-worth, and believe me you are worth it. You are worth it right now, at the exact size, shape, weight you are, in the skin that you are already in.
Be confident in who you are, not just physically but as a person as well. The confidence you have in yourself spills into all areas of your life, not just time spent in front of the mirror. At school or at work, be confident in your abilities! Don't doubt yourself, you are far more capable than what you give yourself credit for! When feelings of insecurity and doubt do come lurking, remember all that you have already achieved or accomplished as a reminder of how awesome you are!
Now go out and rock that confident attitude I know you have inside, remember, life is too short to be anything but happy, especially with ourselves.