Unprotected sex , pills , period missing , pregnancy

Patient: After the 4 days of my gf period , at the date 17 aug me and my gf had an intercourse but it is unprotected . after the sex she taken the unwanted 72 in b/w 3 days after taking pill on date 23 aug she start bleeding which continue to 29 th of aug .Her period date is 10th september but today is 21st september her period is not come . i want to know is still there is a chance that she is pregnent ? because we take urine pregnancy test on 15 september and it comes negative ? and if she is not pregnent what is the reason for late period ? Please do the needful ..! !

Symptoms: Nausea , weight gain , breast size increase , period miss