Thanks for the query.
Emergency pill can alter the menstrual cycle depending on the period of the cycle when you took the pill.
As you took the pill in the second half of the cycle it might have postponed your periods.
As you took the pill within 72 hours of the unprotected intercourse
the possibility of pregnancy
So you wait for few more days, possibly you will get periods. If not consult gynecologist and take tablets for withdrawal bleeding.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429