Doubt about unprotected sex

Patient: Hi, i had an intercourse with my bf on 8th day of my menes cycle without protection so i had taken an ipill. after 7days, i started to bleed which is worrying me very much? What is the reason of this bleeding & how many days it last? I am getting pain in adominal & back pain also Shall i take garuntee of not getting not pregnantAs i have read ipill will give very big side effect on mensytral cycle for several months so my question is how many months of side effects it has approximately? & how it is identified ? How it is cured ?Plz help