Is Pregnancy Possible While On Second Week Of Contraceptives?

OK, I have been on birth control for about 6 months. my periods have never been regular since on them.I get my period on the second week of the pills. However, last month I started spotting while on the sugar pills so i thought it might finally be getting on track. I had unprotected sex while i was on the sugar pills about a week and a half ago. What are the chances of me getting pregnant? Ive been cramping yesterday and today, and this is the usual time i get my period (during the second week of pills) but i havent started. What is up? Im stressing!