Why your stomach get big when breath in?

When you breathe in, your diaphragm contracts and moves downward. This creates more space in your chest cavity, which allows your lungs to expand and fill with air. As your lungs expand, they push against your stomach, causing it to bulge out.

This is a normal response to breathing in, and it is not harmful. However, if your stomach is very large or if it hurts when you breathe in, you should see a doctor to rule out any underlying medical conditions.