I have a stomach-ache.

我胃痛。

youdao

I have a stomach ache. I've had it for 3 hours now.

我肚子疼得很厉害，已经疼了3个多小时了。

youdao

And I heard that you have a stomach illness, is that true?

然后我听说你有胃病，是真的吗？

youdao

The surprising findings have shown a three percent increase in noncardia gastric cancer which affects the lower area of the stomach.

VOA: standard.2010.05.12

Your stomach sinks, you have that sinking feeling in the pit of your stomach, when you get a bad grade on a test.

当你考试考砸的时候,你的胃会垂下去,或者说,会有胃部下垂的感觉

耶鲁公开课 - 死亡课程节选

It's worse for me because I have a stomach problem, Crohn's disease.

BBC: NEWS | School Report | School Reporters' diary

Hopefully they don't have a stomach ache tomorrow.

NPR: No. 8 Louisville Beats No. 24 Notre Dame 73-57

If you don't have a strong stomach, don't examine the bodies too closely.

CNN: Review: 'Syndicate' visuals hamper the fun