DH only ever wear jocks during the day and is nuddie at night and we have a boy, two girls and this one is a boy, so that theory is out the window for us. I think timing worked better for us - DS1 was a surprise so we must have right on time to get him, with the girls we DTD when there was EWCM (which I've worked out I get 2 days before O) and for this one we DTD when I was crampy and it seemed to have worked for us.