Please help me i don't know what to do!!?

hi this is my big sisters profile but she doesn't use it anymore.. i was d by my boyfriends dad.. i went over to my boyfriends house to see if he had gotten over his cold.. he had gotten over it..incase u were wondering.. the family dog got into the house.. my bf put it back out as he put the og back out of the house.. his dad came up to me and said go upstairs i asked why but he said to just go up.. i went up and waited outside the bathroom.. he followed me up.. he told me to go into the bedroom i said no but he grabed my wrist and pulled me in he said if i screamed for help he would kill me.. he pushed me up against the door i told him to stop but he wouldnt.. he ripped my clothes off and smashed me onto the bed.. wen i tried to get him off of me he got frustrated and got a rope and tied me to the bed.. he forced he's inside of me he told me to behave wen i struggled to get out.. he started to kiss me so i couldnt talk.. he called me a tramp and a ***** cuz i dont deserve his son.. i cried and cried and cried.. he forced my mouth open and made me suck his .. he said if i told anyone he would come looking for me and kill me.. wen he was finnally done.. i went home.. i told my big brother wen i got home and he promised he wouldnt tell anyone as long as i told him not to.. my mom means nothing to me i know u might think that sounds bad but u dont know half of what she did i dont really fell comfortable to tell my sister or my stepmom and my dad is a cop he would freak i juat dont know what to do.. im worried that if i tell my boyfriend he will believe his dad and not me.. please help.... btw im 15..