Exactly what Karol said. And to add to that, the days leading up to ovulation are important because that's when you should have EWCM (very fertile) that helps keep the sperm alive for a few days until the egg drops. You want to get BD in the few days prior, and the day of. The egg is only good for 12-24 hours from what I've read but sperm can stay alive inside of you for a few days! Good luck!! Hopefully this is your month! 

It's just because you put in a positive opk test so itll change the first day of ovulation you dont get a positive. So you didnt miss it you actually caught it and since you BD you should be fine! Baby dust to you hope its your month!