This wait is killing me

Andria
I am 12w6d and had the ultrasound to check fluid levels behind baby's neck. With everyone one of my other 3 children I had a gut feeling as to what the sex was and I was right. This time there is no gut feeling. The ultrasound tech said she wouldn't even play into the nub theory though she knew what it was. Any one care guess as to what I am having (and why)?
Waiting another 7 weeks is going to kill me!
Heartbeat was 154