I had hyperemesis as well. I lost 12 pounds the first 4 months of my pregnancy and finally gained 17 back. I was very ill all day pretty much for 6 months of my pregnancy, but after the 4th month my doctor put me on morning suppositories to stop the throwing up. During the 6th month, I would start the suppository, but I craved a regular Coke. So, once I added the Coke and a few Tums to my morning, I was able to eat! Oh boy did I eat.
Every single day, I ate Taco Bell's supreme fries. They don't even make them anymore, but I had to have them. Then, a double Big Mac later that day. Worst diet ever, but at that point I had to gain weight no matter what. I have never ate those fries again or a double Big Mac.