Do you think my brother could be the cause of my anorexia?
Maybe, why do you think he's the cause of your anorexia?
He keeps commenting about my weight and he says that I'm fat.
I see your point, but it's wrong to just blame others for your problems. If you are suffering with anorexia you should be seeking professional help.
I don't need professional help I need my brother to leave me alone.
If you are dealing with anorexia you do need to talk to a professional. It sounds like your brother is not helping you but speaking to a therapist could help you work through your issues and get on the road to better health.