Well, my ex (the father of my first 4) wore undies all the time and we conceived two girls first, then did family planning to get our boy, then the next unexpected bub was a boy too....so go figure???
When we planned for the boy there was certain times of my cycle that we were allowed to DTD etc, everyone thought we were crazy, but it did work and I would recommend anyone wanted a particular gender to seek help from a family planning centre, worked for us, so see what happens.