Could I be pregnant

Okay so my cycle is 28 days my last period was on the 14th of November and ended on the 18th I had unprotected sex on the 24th my fertile window started on the 25th and lasted until the 30th. Yesterday I got some light Spotting way before my period was due again it's not due Until next week on the 14th and with the spotting I had bad cramping worse than normal period cramps but it was in one side of my pelvis....what could this be ?