Hello dear user! Welcome to HCM! I would like to know when was her last menstruation to calculate her fertile phase of her cycle. Emergency pills are used random to stop an unwanted pregnancy and in the most of the cases they prevent it. But since they are pills which contain high dose of hormones the menstrual cycle may change, so periods either come earlier or later than expected. As i was reading you query i didn t noticed any pregnancy test done. So first i recommend you to take a pregnancy test and if its positive for at least twice your girlfriend might be pregnant. If it s negative her periods may be on the way. If she is pregnant you have to consult a gynecologist to discuss what would be the best method to stop it. There are pills used for this purpose but they may be dangerous because may cause uncontrolled bleeding and should be followed by the doctor. If you have any further question don t hesitate write again. I hope you found helpful this answer. Kind regards! DR ERIOL.