Fear about preagnancy

Patient: Hello Doctor, I had a sex with my girlfriend last night. there are 10 more days to her mensus date. i had a sex without condoms. Tomorrow morning i gave her a tablet named prostinor one. doctors advice about that tablet is “Give one tablet after sex within two days to avoid from pregnancy.” But i have a little fear about that thing. is it possible to get pregnent her under these situation? if you can give me a quick reply it will be really helpful to me. And also i want to know is it possible to continue mensus cycle after get pregnent?