Im 13 and uncomfortable with my body

Once i got in to 5th grade people have been body shaming till now and im going into 8th grade next year. My best friends are all super skinny. They all do a bunch of sports like dance, fast pitch, etc. And it makes me jealous sometimes. I always try working out but its not doing anything to body and I was a dancer but I decided to quit to do cheerleading because that was a easier thing to do. I've been bullied about this before by boys and some girls but not a lot. And i know i should feel comfortable and confident with my body which i do feel confident sometimes but I just need to feel more comfortable in my body.