First, good for you you[re still not giving up!
As dfb has said down a few posts -- and what I (in my 8th decade) practice daily -- that just taking care of oneself what is In Your Control: nutritious food (unfortunately too much of what we eat is Not going to give you the needed ENERGY, because it's made up Ultra Processed Food ingredients. CDC or pehaps even Mayo might have reliable info on it.

dfb also mentioned daily strenuous-according-to-YOUR level exercise, something also in Your Control. A variety of stamina, strengthening and flexiblity moves are critical to give a boost tour "tired" feeling.

Finally, you say, you do do "projects" but still do not feel good enough about yourself. I'm at a loss -- unless it's work that you don't Like or has little meaning for you. Even when I used to work for sometime because I couldn't get work in my field, I felt good-enough because I was doing what was still a work helping me stay toward my larger goal: Finding "purpose" as dfb says. This is in fact the most important factor in getting a sense of meaning and fulfillment from work.
Good luck my friend...and i hope you'll reap rewards no less than mine: no doc visits for years, no tests, no surgeries, no meds.