Pregnancy Possibility

I had sex for the first time two days ago. He wore a condom and I even asked him to pull out when he came for extra safety precautions as I’m not on birth control. At the time, I was low fertility, and I have now started my period. Does this guarantee that I’m not pregnant? Yes, I'm aware you don’t get periods when you’re pregnant, but I’ve been a little paranoid about it and I just want to make sure. Thanks.