My bf and I got intimate on 14 december 2014 and he rubbed his penis around my vagina and not inside it. But just for precaution I took Plan B after 28 hours. I had blood spotting (very less) on 30 december 2014 till 2 Jan 2015. My first day of last period was on 6 December 2014 so I am due on 3 jan 2015. I am confused if it was light period or just blood spotting? Also How can I be sure if Plan B has worked?