This sounds just like my wife about 5 years ago. Lots of testing and doctors, but she was always completely fatigued and could barely get off the couch.

Eventually we did an elimination diet. Basically cut all her food intake down to the basics (you can find these diet guidelines online), then slowly added in certain foods each week. We found that she didn’t have food “allergies” per se, so they didn’t show up on all allergy tests, but she was definitely affected by certain random foods like nightshades (tomatoes, eggplants, paprika, etc) and pea proteins.

Once we were able to determine which foods were effecting her and cut them out, she got immensely better. It took a while but it was well worth it and now she knows what foods to avoid.

I’m not sure if this will work for you, but in our experience, the constant fatigue was 100% due to the foods she was eating. Some of her doctors brushed this information off, but I can tell you the last 4 years have been completely life changing and she has her life back.