Can Unwanted 72 Pill Cause Missed Periods?

I used to have normal periods, im 5.8 in height, weighing 65 kgs, ive taken 1 unwanted 72 within 24 hrs of having unprotected sex, and then the next day again another unwanted 72 with 2 hrs of having sex, now i have missed my periods for 2 months, also i have taken a pregnancy test, it shows im not pregnant, please suggest why my periods are late.