Hi K.: My boy was born with a small fetal stomach due to a very rare syndrome called VATER syndrome. His esophagus was actually not connected to the stomach but his trachea was. Unfortunately for me, the ultrasound I had along with amnio, etc., did not show any of this. The only thing shown was a single artery in the umbilical cord to the baby rather than two as normal. The docs told me not to worry however when my baby was born 11/23/06 there were numerous complications but he is now fine at the age of 2 - it took some time and now I am dealing with the small stomach, reflux issues and weight gain but I am not sure whether this would be the same as you are going through right now. My son was 1 in 4000 babies so I believe he is one of a kind but you could bring this up to your doctor and see if they are aware of it.
I think the fact that they have already seen something on the ultrasound shows they are more aware and up to date than my doc was at the time so if you want to chat again, let me know and I can tell you more of what I went through. I did deliver at 37 wks due to fetal distress because there was not enough fluid in the baby as they are supposed to be able to have at 41 wks.
Good luck and my thoughts are with you.