No, well...that doesn't make any sense. You're stomach can't get "fatter".
oO
It's probably that you drink a alot of water, or you just ate shortly before. This means then that it could basically just be a feeling. Nothing else. Nothing to worry about.
Yeah if you drink and eat alot it goes to your stomach first before it gets digested or into your blood stream etc. Its a bit annoying at times during the day sometimes i have to adjust my belt buckle because all of the food and water in my stomach.