Morning after pill problem?

I took the morning pill 2 weeks ago, less then 24 hrs. after having intercourse. I felt no type of symtoms or side effects after taking the pill. Exactly a week last i had my menstrual. I was quite confused because it had come almost 3 weeks early but it was like a normal period. Shortly after I started to have slight adominal pains and still do as of now, i think its odd but this is my first experience with the pill. I'm not sure if this is common happenings after taking the pill or if the pill may have failed?