I laughingly say that it is a lifestyle choice that I did not choose!
I get so tired that on my way home from work (in the subway or tram) I just want to lay on the floor and cry.
I used to take naps in my boss's car when I was a student working in a souvenir shop in Paris (led to all sorts of strange situations...it was parked in the street in front of our shop and tourists would constantly knock on the window to see if I was alive or call the beat cops to check on me...they knew me by then and just watched over me in the end!).
I couldn't make it through the day without a nap...
Now I have upped my protein intake, take liquid Vit B complex drops (absorbs better), hydrate very well (homemade lemonaide with tons of fresh mint, lemons and no sugar) along with all of the other supplements. Doesn't mean that I am not still exhausted but it helps...I also exercise a lot...anti-intuitive but it works...the more I exercise the more energy I have in the long run. (very exhausting at first but it also helps you to sleep better)...
Another thought is a systemic infection. About 15yrs back I was dragging so badly that I could barely function...climbing the steps up the metro or in my building (2nd flr walk-up) had me in tears...hubby would call me sleeping beauty...could not get enough sleep no matter what.
Then I started getting small pimple-like cysts that infected quickly. It took a long time but we got a handle on it (turned out that I had necrosis behind my pouch that was causing a systemic infection) after dozens of runs of antibiotics and treatments and finally surgery I was fine.
It could also be food alergies, absorption problems or a combination of many things...just keep a journal of your efforts and write what helps and what hurts...you may be surgar or carb sensitive too...everytime that I eat either I crash and burn within 20mins. Zaps the energy right out of me to the point that I can no longer eat any carbs while working (I stick to proteins and salad).
No other ideas but I am sure that someone else with have more.
Good luck
Sharon