Can you get pregnant with a little bit of sperm?

I'm 21 but I'll be 22 on October 29th. Long story short, I had sex Tuesday but he pulled out and today I had sex as well (unprotected). The guy had me riding him and I heard him make some noise as if he nutted and I felt a little bit go inside of me. Yet he claim, he knew what he was doing. Obviously.... I know for a fact he nutted inside me. Btw im not on birth control anymore cause of personal issues. So, I stopped taking them. He also said, I was ovulating. Which, isn't the case. Could I be pregnant if he nutted in me a little bit? Also, I would most likely know next month.