Welcome to HCM
We understand your concerns
I went through your description. You must understand that doctors checked everything they can with your husband they were sure that he is normal in every aspects. That is for sure.
Then, why this is happening? I suggest this symptoms are due to unnecessary anxiety
. There are several instances of such symptoms. Mind has a capacity to imagine things including pain and other external conditions. People feel such imaginations as actually happening to them. These can be sometimes called as illusions.
Please take him to a psychologist
/ psychotherapist and get him some good sessions of counseling and psychotherapy
. He should understand that he is normal. Self awareness starts self treatment.
Hope this answers your query. Available for further clarifications.