This question causes a great deal of stress when a non Chinese person asks it of
a Chinese person. A few of my Chinese friends have told me that they are really anxious and undecided when asked this question. So you are not alone.
In China, it is a genuine request for health information.
But in the West is just a greeting.
So if the person asks "How are you ?"
You could respond in any number of ways but usually "I'm fine. How are you ?"
And after that response, the greetings should be over.
If a doctor or other medical person asks you, it is a different matter of course :-)