I took plan B, and read that it was normal to have an early period after taking it. However, I've had too many periods in a short time. My regular cycle starts on the 24th and lasts a maximum of 4 days.

I took plan B July 3rd (3 days after my period ended) then had a period from July 6th-14th. It started again July 20th-24th. And again, today, on the 29th. I've had extreme nausea, migraines, and heavier amounts of bleeding than usual. My periods are generally light and never heavy. Does this usually happen? It's worrying me.
I'm 5'1", 108 lbs, and 21 years old.