Sometimes it's hard for people with health anxiety to accept their symptoms aren't real organic illness. We know that it's 99% likely to be anxiety but it's the other 1% we worry about. Just because you have anxiety it doesn't mean that it can't be some real physical illness.
So what should we do? Certainly discuss it with your doctor and ask for some tests. If as it's almost certain nothing wrong is found and you're still not convinced ask for a second opinion from a specialist. But if after all the tests, scans and appointments with doctors and specialists they all say nothing physically wrong we should accept it.
As I always say: you can't cure yourself of an illness you don't have no matter how hard you try, so why not spend your time curing yourself of the illness you do have - Anxiety disorder?
One trick I've learned, if you have any diazepam/valium tablets then next time you get the symptoms in question take a tranquiliser. If the symptoms subside then you know it's anxiety but if they don't there's still a good chance it's anxiety.
Over sensitised nerves are brilliant at imitating genuine physical illness, that's good to know. But it's only right to be on guard against something genuine, as unlikely as that may be, specially as we get older.