A period missed after unprotected sex, despite various forms of birth control pills

Patient: Re: late period. i’ve been on the birth control pill for years, but at the beginning of this cycle, i forgot to take it for a few days. i started it over again. during my sugar pill week, i had unprotected sex right before i normally would have started my period. i took the emergency contraception pill within 36 hours. i am about to start a new cycle of regular pills, but my period still hasn’t come. could i be pregnant? what else could it be?

Doctor: