Again , this is only small piece of puzzle. No way your doc will find anything with this approach.
Trust me I myself suffer from similar issue and from my experience most docs are " stupid" or ignorant with their approach.
If they don't find any out of the range test ( in very narrow testing) that can be masked with some pills, then nothing wrong with you - keep suffering my friend.
Now talk to your doc see if he is open minded to work with you, or try to find other doc.
Prolonged stress can cause different type of imbalances in your body. Try to look for the root and not the symptom ( the lethargy).