It's actually kind of hard to get pregnant from a BD on O day. That's because the egg lives at most 12-24 hours, and it takes several hours for the sperm to even reach the egg, so the egg could already be dead by the time the sperm reach it if you BD on O day. The best odds of getting pregnant are actually from BD the day before or two days before O. So sounds like you actually have a better chance this cycle!