I caved and we went to one of the elective ultrasound places (yes, the places that pre-pregnant me scornfully referred to as stupid and a waste of money).
We had a 2d sex determination ultrasound, and I could see immediately a tiny pecker between his legs!
Color me surprised because I was SURE it was a girl! But I saw the proof for myself and I wasn't even the slightest bit disappointed to be wrong.
This is going to be a hell of a ride, ladies : )