What Causes Periods Again After Taking I-pill?

hey i m 18 by my age...i had my periods started on 1st feb which ended on 6th feb..on10th feb i had unprotected intercourse...n i took i pill within 2-3 hrs of intercourse...nw after 5 dys i again m haiving periods..i want to ask if everythng is alright..n if it is..m i gonna hv periods again on or around da expected date? my expected dates of periods are from 27 feb to 1st march..plz write to my querry at the earliest..