Hello Ladies, I have a question

My boyfriend and I had sex yesterday. I’m not on Birth Control, but we do use condoms.

We went two rounds. The first round everything went as planned. He finished inside of the condom & nothing leaked out. However for the 2nd round, we took a 10 min break & went at it again with a new condom.

However, twoards the end the condom somehow slipped off inside of me & he was inside of me raw for about 20 seconds. He didn’t clean himself or anything between rounds so he’s scared because although the condom itself didn’t have semen in it or anything, he still had on his penis from the round before.

I already passed my ovulation day & my period is expected to come next weekend. Should we be concerned? How likely is it that I can get pregnant & how would I know?