What Causes Heavy Bleeding Before Periods Are Due?

Last Wednesday April 20 I had unprotected sex (without a condom). Even though I am on Nuvaring I was worried that he ejaculated inside me so I took the morning after pill on Thursday April 21. Starting Yesterday April 26th I started bleeding heavily. My period isnt suppoded to be for another week. Could this be and early period and should I take out the Nuvaring?