What Causes Vaginal Bleeding After Taking I-pill Followed By Unprotected Sex?

hi .. i had an unprotected sex on the first day of my period,and today is the 5th day m still bleeding. usually my periods get over by 5th day and there is very less spotting. but right now the flow is still like 3rd day. is it becoz of i pill. till how many days it will last ?