Why Haven T I Gotten My Period After Taking Emergency Contraception This Month And Last Month Despite A Negative Pregnancy Test?

1:7 PM I had sex on 14th march and the same day i had taken ipill and that same day itself i got my periods then on 21 i had sex and had taken pill that say itself then after 4 days i had bleeding which lasted for 2-3 days. On the month of april on 2nd i had unprotected sex bit he didn t cum inside then again on 6th i had unprotected sex and on that day itself i had bleeding which lasted till 9th. On 10th i had pregnancy test done which came negative but I haven t had my periods yet for the month of april and its already may now. Why? Whats happening to me??