Hi There, The First Day Of My Last Period Was

hi there, the first day of my last period was the 4th of September, had unprotected intercourse on the 21st of September, my cycle is about 30-32 days (been monitoring for the last 6 month), got negative pregnancy test. Tonight just feeling some short (few seconds) sharp pain on my pelvic area. I don't feel the usual cramp like if I was going on my period. Any advice / thought of what is going on with me?