There are so many things that can cause body image issues. Unrealistic beauty standards, social comparison and past trauma are predominant causes of body image issues. When you constantly push yourself to achieving perfection, it will create a feeling of inadequacy which will trigger body image issues.
It's very important not to tie your self worth to your appearance because it makes self-esteem suffer. For me, I try to challenge toxic messages and embrace my uniqueness and that's how I was able to deal with negativity.