It will grow bigger momshie don't worry. You still have 10 more weeks. I have the same situation, my body is just a size of an average person not too thin, not too fat while I was pregnant I just looked like bloated or I ate a whole chicken. My OB said to eat more and more in order for me to gain weight.
They said that if the stomach is much bigger it could only mean that it's full of water, while the small stomach has a pure baby inside.
Maricris Gutierrez