I took ipill within 72 hours and now my period is more than 2 days late from my expected date

Hi doctor, 

I took ipill within 72 hours and my periods were due on 6-Nov, but now it's more than 2 days from my expected date that I have not got periods.. Pls tell why my periods are late... What should I do to get my periods???? I m tensed... My legs and back is paining like anything..