DH used to always insist that I was on top, so of course as soon as I moved afterwards, all the spermies would come out, which isnt much help. The first time we did it missionary around O time, I actually didnt lose any spermies, and I also put a pillow under my bum while we were doing it and also didnt get up for the rest of the night and I ended up getting a BFP. That was the first time that I didnt lose spermies.