Weird Period...

I usually start my period with some spotting and the next two or three days it's really heavy. It usually lasts about 4-5 days and the last day it's just spitting again. It changed now for some reason, I've been spotting for the past 2 days and the 3rd day was somewhat normal but not like usual. Still spotting today... 
I did have rough unprotected sex about 2 weeks ago and took a plan b pill, which is what I usually do and my period isn't this weird . Are the pills finally having a different effect on me? Or could it be something else??