Can Pregnancy Occur Despite Taking Postinor-2?

sep 2010 i took i had my normal periods then the same month i had unprotected sex and the following day i took postinor 2 after 5 days of taking the pills i had unprotected sex which led me 2 taking postinor 2 again.then on oct 1 i had my periods again...which they came from 1_4same month on 5 i had sex but protected but my husbund ang i came to realize the condom busted which we both feared n on 6th i took the pill again and after 4 days i got a bleeding on 11th_13.on 16 i had unprotected sex and 17th i took the pill..im worried so far can i be pregnant?