That's actually very common from what I've heard. The 20 week u/s isn't really to find out the gender, that's more of a bonus (I've learned and yes it is very frustrating! I'd love to know the gender right now.. check out my topic in "second trimester". I'm due May 19th, only a little earlier than you and had this whole frustrating discussion with the u/s tech. I live in SD now, but it was the same thing when I had my son and we lived in FL, they said we had to wait till at least 20 weeks (I snuck in at 19 though!) and that it wasn't really to find out gender, it's to make sure baby is healthy, and all the measurements are on track. At any rate, I feel your pain and good luck!!