Took unwanted 72 after having unprotected sex no periods

Patient: I had unprotected sex with my fiancee on 15 Feb and on next day in morning she took unwanted 72. On 25th Feb she had light withdrawal bleeding which lasted 2 days. Her next period was due on 5th March but its more than 10 day i.e. 16th March and no periods yet. She took ican pregnancy test on 15th march which came out negative. Is there any chance of pregnancy ? We both are worried please help.

Symptoms: No periods