In my dreams i write insulting words on my body?

What a waste of dreaming time.

In my opinion, you shouldn't overthink it, dreams can be really confusing and weird, they may or may not be mirroring your thoughts.
Like I said, I wouldn't overthink it.

Could be a fetish thing, some people are into humiliation and body writing.

Dreams can be completely erratic and irrelevant to real life but it can also reflect subconscious thoughts or feelings. If you feel like what happened in the dream is based of something you really think about yourself, it might be good to go see a professional. However, it could also be possible its just a random dream that has no implications from reality.

Why do you think you hate on yourself in your dreams?

Do you have any insecurities?

I do that in real life.