Yes, it may have happened....women can bef fertile up to 48 hours after they ovulate. Unfortunately...now the wait is on! Good luck!
I'm not sure if all ovulation tests are the same, but I know that at least for Clear Blue Easy, you should ovulate 24-36 hours after getting a positive OPK. So, that means that you could have ovulated on the same day you had sex, so yes, you could get pregnant.