I dont have solid references for this, but i recall hearing someone talk about the residual effects of covid spike proteins, and long term fatigue. They were suggesting taking Ivermectin for a week.
I had a similar experience, and never took the vaccines. I didn’t do ivermectin, I did high doses of vitamin C for a while, and then started taking 5000iu of D, plus zinc, and 500mg of magnesium per day. I also cut out almost all refined sugar in any form, and started eating unrefined food. After about a year, the lethargy faded, and my energy came back.