I'm so worried because i'm not sure if he mistakenly ejaculated inside me especially knowing that I ovulate the next day..will the postinor 2 prevent me from getting pregnant?

Hi,I'm worried,I had oral sex with my boyfriend on the 15th,no penetration but we were both naked and he ejaculated on top of my vagina and I was to ovulate the next day being 16th..I took two tablets of postinor2 an hour later..