Thanks for the query.
If you took the emergency pill within 72 hours of the intercourse, that might have given protection against the pregnancy
Emergency pill can alter the menstrual cycle depending on the period of the cycle when you took the pill.
If you took the pill in the second half of the cycle, that can postpone the periods.
So delay in your periods could be due to that.
It can also present with side effects like intermenstrual spotting, pain abdomen etc.
Usually these symptoms will subside soon.
So wait for few days.
If the spotting and pain abdomen persists or increases, better to consult gynecologist once and take symptomatic treatment.
If you didn't take the emergency pill within 72 hours of the act, go for pregnancy test once.