Oh, by the way, I've heard of doctors telling you to eat more calories when that happens. So instead of a 2,000 or 2,500 calorie diet, you'll probably be asked to eat 3,000 calories a day.
My SIL didn't gain anything during her pregnancies and actually lost weight instead! Her babies were born on time, healthy, and are still healthy as children. I don't know WHY it is happening to you, but I know that it doesn't mean something will be wrong with your baby. Continue to eat and take your prenatals, of course. Your baby will use your fat stores to grow and develop.
I've heard that it can be normal to actually lose weight during pregnancy. Your body is using and needing more and more calories b/cuz you are eating for you and your baby. It is also hard to eat a lot when you are nauseous. Don't be too hard on yourself. It sounds like you are doing everything that you can do right now. I am sure that your weight will pick up. That's sure to come. He, he. The first trimester can be a little scary. If you think that you're losing too much weight, voice your concerns to your dr. and maybe he can give you something for the nausea, so that you can keep down more food. Good luck!