How can i not care what people think and be happy?

i'm fat over weight and i find myself ugly... see i can sing in front of millions of people cause i love to sing and i love looking pretty but unlike singing if i put a tad bit of lipstick on and go school i'm thinking why did i do that?!?!?! i also freaked out when i got my hair dyed i'm depressing to people i hide my feelings cause i'm always sad i don't want to care what people think of me i wonna get over that and then maybe i can work on my weight more with out feeling scared of being judged how can i get over my fear or what ever you call it?