Had protected sex two days ago. after sex i had bleeding it stoped but now im having cramps like im going to start my period but wont start for 2 more weeks. He was bigger than i am used to so could that be the cause? there was pain during sex as well but it went away after a few minutes. I had back surgery 6 1/2 months ago and this is the first time that i have had sex since then. what is the cause of the cramps and bleeding?