What would you do if your boyfriend kept saying you're fat?

I'm starting to get pissed off... obviously i'm eating for two.. before this i would usually never be able to finish anything i ate so my boyfriend would finish it for me. Ever since i've gotten pregnant he keeps calling me fat.. even when he records his snapchats "fat ass bitch" like why thooo.. and believe me he KNOWS i dislike it and i make it known every time he does it that it pisses me off. I honestly looked thru his instagram a few times cause i have a really unsettling feeling and i've seen him search up girls but later on it will be deleted.. i've deff ALWAYS been insecure about myself before i meet him but all these girls are skinny and not for nothing i know i'm not hideous but i'm no where near as beautiful as those girls so it makes me feel some type of way about myself. I've also already had a convo with him about that which is why he thinks hes slick deleting it.. i already know i should just leave him so idek why i'm writing this. I guess i just need to get it off my chest but ugh idk man it's hard i just never feel good or pretty enough. It hurts.