Chance of pregnancy?

So I have a very regular period, it mostly always begins and ends on the day that my calendar predicts, if not just a day to two days early/late. But for the past few months, it has began on the day that the calendar predicts. I wanted to have unprotected sex with my boyfriend since it was the day right before my period was predicted to begin, and I let him come in me. My period arrived today, but is there still a chance of pregnancy even if it still comes? I know sperm will die 2-5 days after being in you, but I’m just curious to know. I don’t take birth control, either. But he and I both understand and accept the risks.