I think you still have a good chance of having a girl. What you described sounds like the Shettles method, which I believe is based on the fact that male sperm swim faster but don't live as long as the girl sperm. So if you bd close to O, I think the theory is that the Y-chromosome spermies have a better chance of winning the race and you get a boy. If you bd a few days before O, the boy sperm are already dead by the time the slow but hearty girlies get there and catch the egg.
But there are millions of sperm in there and I think many factors influence which one "wins" the race. We also bd'ed near O (I think on the actual day) so I'll be curious to see if this is a boy!
But there are millions of sperm in there and I think many factors influence which one "wins" the race. We also bd'ed near O (I think on the actual day) so I'll be curious to see if this is a boy!