I've had intercourse with my gf last month on 29th night, and few times too i.e. 29/9/2017 during her period. Her cycle is usually 27-30th of every month. She had her last period on 30/9/2017. I gave her unwanted 72 within 36 hours of intercourse. But there was no withdrawal bleeding neither any period till date. Is there any chance of pregnancy or is it just the effect of using contraceptive pills?