Is there an idiom with "stomach" that expresses one's concern/worries about something, something like "I got so worried that my stomach hurts" & stuff?
You could use the expression:
Fig. the middle of one's stomach; the location of a "visceral response." “I got a strange feeling in the pit of my stomach when they told me the bad news.”
(McGraw-Hill Dictionary of American Idioms and Phrasal Verbs)
The adverse stimulus can be described as stomach-churning:
ADJECTIVE If you describe something as stomach-churning, you mean that it is so unpleasant that it makes you feel physically sick.
- The stench from rotting food is stomach-churning.
- ...that rush of stomach-churning fear at the sound of a mortar exploding nearby.
As with Cobuild's second example above, example sentences from Longman show the at least partially metaphorical broadening, certainly involving dread:
• For much of the past week I have had this dreadful, stomach-churning feeling of imminent disaster.
• At the end of every set of three levels a stomach-churning guardian awaits.
while Macmillan highlights the dread-inspiring nature:
- stomach-churning: making you feel very frightened, nervous, or ill
“To worry oneself sick [about or over something]” is one – the word “sick” implies a state of nausea or illness.
“I worried myself sick about the exam results.”
“To be sick to the stomach of/with something” = to be irritated and annoyed by something but this is old-fashioned and is now reduced to “to be sick of/with [a repeated action]”
“I am sick to the stomach of your constantly complaining about everything I do!” (old-fashioned)
“I am sick to the stomach with your constant complaints about everything I do!” (old-fashioned)
“I am sick of your constantly complaining about everything I do!” (Current)
“I am sick of your constant complaints about everything I do!” (Current)
Have one's stomach (tied) in knots
used to say that a person has an unpleasant and tight feeling in the stomach, usually from nervousness
Her stomach was (tied) in knots as she awaited the start of competition.
Have butterflies (in your stomach): to feel very nervous, usually about something you are going to do.
Example: I had terrible butterflies before I gave that talk in Venice. (Cambridge English dictionary)
Another expression I don´t see mentioned is "turns my stomach" - e.g. "Seeing something like that really turns my stomach". The general meaning is that it induces nausea, stomach agitation, or makes one want to vomit due to being distasteful or disgusting.
Variants are "makes my stomach turn", "turns one's stomach", etc. Reference: https://dictionary.cambridge.org/us/dictionary/english/turn-sb-s-stomach
Another common idiom would be
[This bad thing] made me sick to my stomach
Finally watched "Bombshell" and it made me sick to my stomach.
'Cannot stomach x,' is often used to represent x being too hard to handle (usually for a person).
For example, 'Johnny was never a good soldier because he couldn't stomach killing.'