Nausea can be from more than just not eating enough, but it can also be from dehydration. Dehydration is a big cause of preterm labor for many women, so you want to be sure to drink about a gallon per day. Nausea can also occur if you're overtired, stressed out, depressed, or any other number of things. If it persists and/or gets worse you should talk to your ob about it. I had morning sickness right up until delivery day with all 3 pregnancies, and at the worst, phenergan helped a bit.

I also just thought that it could be acid reflux. I mistook a lot of reflux for morning sickness, and when my ob gave me zantac in my 3rd pregnancy it helped dramatically.