Thanks for the query.
As you took the pill within time, the chance of pregnancy
Emergency pill can alter the menstrual cycle depending on the time of the menstrual cycle when you took the pill.
Once the cycle gets disturbed it will take sometime for regularization.
So you once go for pregnancy test. If the test comes negative, wait for few more days possibly by that time 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