severe pain before periods,on regestrone

Hi, i have been having irregular periods for last 2-3 years. the doc did internal check up and said everything was normal ,very slight PCO's.not big enough to undergo medication.She put me on regestrone for 20 days,2 tab's a day.got my period on the 3rd day after discontinuing regestrone.Had very severe unbearable pain and cramps before actually starting to bleed.nauseous and dizzy.periods lasted only 3 days and slight pain the abdomen still persists.I have not been using protection for a few months now. Could someone help me understand if this could be pregnancy?