What Causes Prolonged Vaginal Bleeding After Having I Pill?

Hi..my periods got over on 14th march 2015 and I had unprotected sex on 16th march,2015 and had I- pill on 19th march, 2015.. Since 25th march 2015 I am having vaginal bleeding as a side effect of I pill for 6 days now(30 march 2015). Can u plz tell me when is it going to stop and will my regular periods be irregular?