Fatigue is miserable. My first thought upon reading your update is that your depression might manifest as a very physical depression. In all my years of being in the mental health system I've noticed that for some people, depression is a very physical disorder. The challenge is that (in my experience, anyway) psych meds (except stimulants) cause tiredness. So if one is depressed - tired...and on anti-depressants - tired.

I'm on several meds and I sleep at least 10 hours every night, plus I often have to lie down during the afternoon for half an hour because I feel exhausted. I go to bed by 9:30 - I feel like going to bed at 8, but I don't allow myself to.

If I worked the schedule you're working I would be exhausted.

I wish I had some great advice for you, I feel so bad for you. All I can think of is trying an antidepressant and hope that after a few months of treatment you feel less tired.