Pregnant from period sex?

Hi everyone, I know it's possible to get pregnant from having sex on your period, it's just unlikely. My bf and I had sex the last day of my period and he came inside of me. I've been feeling nauseated randomly the past week or so. My period ended on the 5th. I'm only 20 and my mother is super conservative, we never talk about these things. The nausea feels like it's deep in my tummy and it comes in the morning or at night sometimes randomly during the afternoon. Please help! Not sure what to think.