What Are The Chances Of Getting Pregnant Without Ejaculation?

sir i had a intercourse with my girlfriend on 6th feb.(6:00 P.M) and her periods are due on 11th feb. she had taken unwanted-72 at 8th feb. (4 P.M), now she is not having her periods, i had not ejected my sperm inside completely.
tell me whats going on.....?? plz tell when she should test her pregnancy with strips...