How far along are you in your pregnancy now? Are you seeing someone for prenatal care at all? It's not at all uncommon for a lady to lose some weight in her pregnacy in the first trimester. If you follow the textbooks, you're supposed to gain about a pound a week on average after that, for a total weight gain of around 30 pounds. But I have known some ladies to gain 20 pounds and push out these 8-9 pound babies!
I wouldn't worry about your weight too much as long as your baby is growing. You can measure this yourself if you want to.
Blessings and pats on the tummy (ooo I love babies!),
-Donna