Ovulation

So I ovulated on the 18th for sure ( I tested) and I had unprotected sex with my bf. We also used preseed that day. He works a lot so that was the only day in my fertile window that we were able to baby dance. However we also had sex on the 20th ( twice) but I took a opk that day and it was negative. But I did read online that it’s possible. If I were to get pregnant this cycle would it be from my ovulation day or on the 20th. I just want to be exact,