Plan B, bleeding

I had my period February 9 or 10th (I can’t remember exactly which day it started) and the last day was 15 February. I ended up taking a Plan B on 17 February had nausea the next day, which I know was one of the symptoms because I read the box but about three days after that I started bleeding (also know that is a symptom) . And now ever since I have been on and off bleeding anything from the light to a super heavy flow… has anyone else had this happen? Any idea on what I should do?