It's not too late at all! We are also a couple that couldn't BD all the time, so figuring out timing was important. We TTC for a year, and had so many tears and and so much stress along the way due to worries about DTD on the right day. Finally, after a year of frustration, I decided I was done freaking out. When I got my positive OPK a couple days early, I was a little irritated because there was NO way to take care of things that night. I didn't get super upset, though, because I'd kinda let go of things at that point. My DH came home from work the morning after I got the positive OPK and we had sex, but I want feeling super confident about it. I figured I was at least in with a tiny chance... I definitely wasn't getting my hopes up, though! And wouldn't you know it? That was the cycle that I finally got my BFP. We DTD *once* within my fertile period, and it was the day after my positive OPK, at that. Crazy business!