My twin sis. and other members of the family keep pitting me down?

i have a twin who is always callin me names like ugly fat and pig and for some reason she calls me fat apartment lady? she always trys to be better than me. i am chubby but so is she, she weights the same?! then when i try something on she pretends to giggle and make fun of me, and she and mom whisper or laugh at me. shes always pushing me aroumd and getting in my stuff then when she tells me im ugly i say we look alike and she just says you wish im sick of it! same with my brother hes always saying rude things to me they are the reason i have a very loe self esteem i wont even start caring a purse cuz i know they will laugh at me. i feel worthless and fat i dont even feel like a girl sometimes cuz i imagine myself butt ugly :( i cant get away i have to share rooms with my twin plz help