Dealing with Body Shaming from a Family Member

my grandfather tells me constantly i need to go on a diet and that i’m too fat, that i “need to do sit-ups and get contacts and i’ll be hot”. i weigh 145lbs, and i’m 4’10”. he’s the reason i’ve had an eating disorder and body dysmorphia since elementary school. everytime he says it, it sends me into a mania where i can’t even look at myself in the mirror without crying, and i just want to go back to harmful habits i’ve been clean of for a while. due to circumstances, i live with him and can’t really get away as much as i want to. i don’t know what to do anymore.