Is it correct to answer with "that's not it" in this dialogue
- You look bad. Do you have troubles at work?
- No, that's not it. I just feel a little exhausted.
"Do you have troubles at work?" sounds a little unnatural to me. It sounds like the sort of thing I expect to hear from a non-native speaker who is translating literally from their own language. More natural would be "Are you having problems at work?"
I also don't really think you can be "a little exhausted".
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.
Thanks for your answers.
Can I use "it's not that" instead? If I can, what would be the difference? (to me it is like changing stress from the object to subject).