Taking pill menstrual cycle date delayed

Hi Sir,      

Myself and my girl friend had unprotected sex on 6th day of her menstrual cycle date. After sex she took emergency contraceptive pill.Now she missed her period last month and this month(2 months). we checked last month and this month with urine pregnancy test she's getting negative results.Why she's not getting her date. If she is pregnant when it will be conformed (which month). Please help us                     

Thank you