What Causes Vaginal Bleeding On Taking Unwanted 72 Pill?

I met with gf on 13th Feb and the condom was failed,so she taken tablet unwanted 72 after 5 hr and after 6 days bleeding occured, 17th Feb bleeding observed, when bleeding ll stop and what to do to stop bleeding and is there any effect?? ,and the last period stop on 11 Feb,when ll b d next period date expected??nd its periods too early? ll periods occur normal nex tym?. plz let me know