Can you get pregnant right before your period starts?

Catherine

I had sex without protection with my boyfriend on Saturday night, thinking that since my period was due to start the next day that it was probably fine. I need to know if I am mistaken. I figured that since ovulation day was long gone that everything should more or less be fine. My period has since then not started and I want to know if I should take this seriously or if I am worrying over nothing. Thanks for your responses, please be kind.