Welcome to HCM
We understand your concerns
You are a healthy man as you told. You might also be wonderful and disciplined and punctual. You must have been very much perfect about your work. Now you are retired. That might be the cause of the problem. You hate to sit idle or passing time just like that. You want to be engaged. Am I correct?
There should not be any problem with you because doctor could not find any. They are the best judges of your condition. Every doctor in your are cannot be wrong. From the symptoms you mentioned, no conclusion is rather possible. Seems that you are perceiving troubles. Please consult a psychologist
for help. You might have a mental condition (not disease). Good luck.