random bleeding?? help

I ended my period on the 12th of January, unintentionally had sex with my man on the 13th (not long, couple strokes) he finished outside of me but I still took a plan B. ( I took a plan B December 30th for the same reason). It’s now January 18 I am RANDOMLY bleeding? probably a side effect but could it be my period AGAIN? Or is it really just a side effect from the pill?