Can Taking Plan B Lead To Early Menstruation?

i had my regular period on september 14, a week later i had unprotected sex in the late night, so the morning after i took plan b. a week after that i got my period again on the 27th in the same month. its been a month now and i still have not gotten my period. n i took a pregnancy test last week and it showed up negative really quick. am i pregnant?