Hi , I Was Supposed To Have My Period On

Hi , I was supposed to have my period on May 14 it never came so i thought it was going to come on the 21st because through out my life my period changes different dates. But this May it never came at all. I had sexual intercourse this Sunday that just passed and yesterday in the afternoon I went to the bathroom and a lilttle blood was on my under wear i thought it was my usual vaginal discharge so i put a heavy tampon when i got home and I jad it all night until today at 6pm do i took the tampon off and it was just cover with dark brown on it. My right ovarie hurts a little bit like when im about to have my menstrual. My fiance says im pregnet but i just dont know.