Self esteem

How do you stop caring about what other people think of you? I feel very self conscious that not many people are self conscious about. I'm self conscious about my round face, how I'm too skinny and my ankles. Yes my ankles. Life was fun before I became insecure. I feel like I can't wear clothes or certain hairstyles without feeling horrible about myself. Little by little I stopped caring (I used to hate my nose and thigh gap) but I want to get better I really do. I've been trying to gain weight, build up muscle but I still feel ugly. I feel like everyone is judging me and my friends don't make it any better. I make fun of them back but regret it so much later. They call me skinny and make fun of my face. But at the same time they always have my back and make me laugh so much. So, how do you stop caring of what other people think of you?