i started bleeding during sex, kept on afterwards so much i

i had sex last nite without a condom and we were having sex for about 20 mins and when we were finished i went to the bathroom and had blood all over me. it was the bright red. i was with this guy last weekend and this didnt happen. we have been together before several years prior and never had this happen. i am in the middle of my cycle, the 14th day of my cycle will be monday and he did ejaculate inside of me. their are no signs of infection, i have been down that road, and i am not sure whats going on. is this just cause i might be ovualting? (i am not on any kind of birth control) do i need to 2 go see my dr? thank u 4 reading pls help