Vaginal bleeding. Why it happens to me?

After the intercourse on 15 sep i noticed there was heavy bleeding from my vagina it was my very first time before that we have tried for two times but it doesn't penetrate and one time there was small amount of bleeding but on 15 when the penis was fully penetrated in my vagina i feel that something in liquid was flowing and when i saw it was heavy blood flowing and it for hours then i was admitted in hospital for 4 days doctor asked me what happen i told them whole situation they also asked me if i have taken some medicine but i didn't take any medicine about a year ago i take one unwanted 72 in my confusion and fear even there was not penetration..now am at home and my health is better i want to ask that this will happen every time i have sex because it's my first time it's like a nightmare am so scared and i have pcod so please tell me does it happen every time i have sex because it's freak me out please help me ?? It's a big concern for me please help why it happens to me ??