I've got a tight feeling in my stomach.

我觉得胃部胀痛。

《牛津词典》

The pain started in my stomach and radiated all over my body.

我起初只是肚子疼，后来全身都疼。

《牛津词典》

I had a few butterflies in my stomach.

我心里七上八下的。

youdao

I would be grateful if you would wait until that point if at all you possibly can. It just makes the whole thing work a little easier and it prevents that drop in the pit of my stomach when I see half of the class leave.

我将感激不尽,这样会好一点,以免我看到半数人走掉时,心情会受到影响。

耶鲁公开课 - 1945年后的美国小说课程节选

The children were oddly trusting, offering huge hugs and burying their faces in my stomach.

WSJ: Getting Into a Character

But I had to learn to put my pride aside because it wasn't putting any food in my stomach.

NPR: Escaping Hunger: One Man's Story

Shortly before then I had turned down an offer of home-cooked delicious lunch by my wife in order to have enough free space in my stomach for the anticipated banquet.

BBC: African viewpoint: Christmas in Lagos