last year i took the morning after pill about 18 hours of having unprotected sex. a week after i had a very light period. one month went by and no period. i took 5 pregnancy tests and all negative. second month came by and no period. third month came and still no signs of it. Untill the fourth month i then got my period! yes four months after taking it. didn't even spot or anything...i was really freaked out! But don't stress it if months go by and take pregnancy tests and all negative. These are side effects of the pill. after that i had my period on a regular monthly basis.