Patient: I started my period on Jan. 2nd and ended on the 6th, today i started my period again. This is very unusual for me. My periods are very regular, lasting only 4-6 days. On the 6th I had unprotected sex and the guy “came into me”. Within 24 hours I took the Plan B pill and 12 hours later took the second one as the directions said, could that pill cause me to start my period again?