Hello sir, i had sex on 1st of last march 2013 and i had unwanted-72 tablet next day by 9pm, my previous month's came on 7th of march but i didnt got my periods this month, today is the day that i used to get my periods accordingly. what may be the reason, kindly suggest me sir. my age is 25yrs. Today i checked with Rambaxy pregnancy testing kit but it came negative result. I dont know why i am not getting my periods yet.