How too gain confidence.?

I'm not a confident person. I used too be, but now times gone on, i'm not. I'm 14, now. I know, it's because i'm growing up.. or something like that. But i want some help. I HATE my weight, i feel like im different from my friends, i'm quite good in school. But, there's more better people. I feel like i don't fit in. My friends keep saying i'm not fat, but i don't believe them. I have no pride in my work, if i don't like it i rip it all up. Ive never been bullied, i don't wear make-up because i think i don't suit it, and it makes me look more ugly. I never do anything with my hair, i just normally tie it up. I'm always out with my friends. Some of the boys think i'm ok looking. They say, 'theres better & worse'. My mum does trust me, but not as much because i never ate my lunch, i lost weight, & but not enough that i was comfortable with. I would just like confidence to go out, make some new friends. I just want some help. Maybe some websites? Thanks xx