Why does my brother hate me so much?

I am overweight and i acknowledge that but all the time my brother calls me a fat worthless hog. If he keeps it up im going to go back to cutting my wrist (stopped for 4 months) One time he even said im a waste of gods creation. i don't know what i did to him for him to hate me so much. And when i make up my mind to lose weight he just brings me back down. Today day he said " **** you, you ugly *****" because i wouldn't get him the pliers my mom said hes jealous but i don't think he is hes slim with good clothes and alot of Friends i have one. My mom does nothing about it. Im also in counseling for ptsd(post traumatic stress syndrome) but when my self confidence goes up he knocks it down. I see all the pretty girls on the web and i wish i was them. How do i get him to stop??!!!!! because soon i dunno what im going to do to myself