Im being “cyberbullied” by some little kids in elementary school that barely know me

One of my best friends, male friends and two of his friends have been “cyberbullying” me. They have been calling me “fat” and “big back” and other things like that for absolutely no reason. I barley know these kids and they have something against me. I have been struggling with thinking im fat myself and this is not helping. My best friend was private texting me saying “end their whole career” “roast them” etc and I cant. Normally being called names dont hurt but for some reason this really does hurt.