I Took A Plan B Pill On October 21, 2016.

I took a plan b pill on October 21, 2016. The first day of my last menstrual cycle was October 12, 2016. It last for six days. I took the pill 3 hours after sexual intercourse. I took an early pregnancy test yesterday and it came back negative. I have not started my period, and would like to know why i haven't and if there's a chance i could be pregnant.