Usage patterns
胃が痛いto have a stomachache
My stomach hurts from stress.
胃が弱いto have a weak stomach
I have a weak stomach, so I have trouble with greasy food.
胃を壊すto upset one's stomach
I upset my stomach from overeating.
胃に優しいgentle on the stomach (of food or drink)
This soup is easy on the stomach.
胃がもたれるfor one's stomach to feel heavy/queasy
My stomach feels heavy after eating too much grilled meat.
Expressions
胃袋をつかむwin someone's heart through their stomach; attract someone with food