Periods related issue. My concern is!

Hello Mam ..... I m 23yrs old ....my concern is regarding delaying of my periods...... On 2jan,2019 i had  unprotective sex after that i took the unwanted 72( within 72hrs as prescribed)......Again on 2nd of February i had unprotected sex .....and i took unwanted 72(as prescribed within 72hrs.......... On 10th March...i had protective sex and want to tell you that during intercouse i bled heavily ............ Now this is 30th of April )....... And during the entire date i had 3 times pregnancy test ,it was negative all the time and i had checked even today which came negative............. So my greatest concern is about why m i not having periods?????? It is been 4months....i missed my periods.......i want to know the reason behind this.....and also how to fix my periods?...................so kindly help me mam to fix the worries that i had till date regarding delaying of periods...