How to boost my confidence?

I'm a 16 yr old girl in the UK. I've got a good groupa friends n I'm very sociable. When I'm out I kinda put on a front of being some loud, outgoing girl but I dno why. No one would believe I have confidence issues but I do, I just hate everything about myself especially my body as I'm overweight. I just wanna know how I can boost my confidence about myself in some way..