Please state in which country your phrase tends to be used, what the phrase is, and what it should be.
Example:
In America, recently came across “back-petal”, instead of back-pedal. Also, still hearing “for all intensive purposes” instead of “for all intents and purposes”.
You don’t feel “nauseous” you feel “nauseated”.
EDIT: TIL “nauseous” can be used in place of “nauseated”. This usage has been common since the 20th century.
It appears both are correct. From merriam-webster:
TIL just because some people use nauseous to mean nauseated, you don’t know just from looking at them who’s who, so better use nauseated just in case to be safe.
Is it correct to say “I’m nauseous”?
In that case I think it’s ambiguous what you mean. I’m guessing you mean to say “I’m feeling nauseous”.
Or they could mean “I’m feeling nauseated”. Impossible to know without context, but more likely they meant “feeling like I might throw up” vs “feeling like I might make others feel like they might throw up.”
My attempt to disambiguate was to add the word “feeling”. I suppose maybe you could “feel” like you are nauseating others. This is part of the reason I like to be precise with word choice.