How do I have a flat tummy?

I’m 165cm & 56kg female. Waist line is 32cm. other part of my body it look normal just having a big tummy. It look as though I’m a few month pregnant but I’m positive NOT pregnant.

Every time after meal my tummy will swollen. Even if I’m thirsty I gulp lots of water in one time my tummy will be swollen as well.

Beside exercise or balance diet what else I can do just to have a flat tummy??? Tired product to reduce my tummy fats but cant help much.