Can Missed Period Be Symptom Of Pregnancy Or Irregular Period?

IRREGULAR PERIODS, HAVE BEEN TOLD I HAVE PCOS. JUST HAD A BIOPSY IN MAY, RETURNED WITH GOOD RESULTS. WAS TOLD IF I LOOSE SOME WEIGHT (APPROXIMATELY 30 LBS) MY CYCLE MAY BEGAN TO REGULATE ITSELF. I HAVE LOST ABOUT 30 LBS. AND NOTICED MY CYCLE CAME ON THE LAST THREE MONTHS SAME TIME, STAYING ON FOR 5 DAYS AND GOING OFF. HAD UNPROTECTED SEX 2 DAYS AFTER MY LAST CYCLE. THIS MONTH MY CYCLE IS 3 DAYS LATE. COULD IT BE BACK TO ITS PAST IRREGULAR CYCLE OR STRONG POSSIBILITY IM PREGNANT?