What Could Light Bleeding With Cramps Soon After Normal Menstrual Cycle Indicate?

Hi, I had unprotected sex and took plan b the next day. The week after that, I started my period (regular time) 6days of my period. The week after my period ended, I started to have bad cramps and a light light period again which lasted 2 days. I am still having cramps and it Is the 4th day having them.