Ah...the million dollar question...;)
This can be the most frustrating and and confusing aspect in regards to our health anxiety!
Keeping in close contact with your doctor as far as having check ups and making sure you are pronounced healthy and not at risk for any physical issues is of course recommended...
...and working on managing your anxiety, and learning how to lessen symptoms through coping skills will also help you in recognizing and controlling the 'false alarms' that panic often brings our way.
Using an anti anxiety med is helpful for some as well. It is becomes very obvious that physical sensations were brought on by anxiety and not a health episode when your Rx knocks it out in minutes!
Here is a tool that you may also find helpful. It illustrates the anxiety=symptoms=more anxiety=more symptoms cycle...check it out for reassurance that your question is a common one, since we all go through the same experience and though process!
Health Anxiety- The Super Scanner
http://www.get.gg/docs/SuperScanner.pdf
Peace and progress!
S.C.