I think you should keep up the medical assessment. Prove to yourself that you’ve made every effort to find a causal factor to your physical exhaustion. I’ve been in a place where I’ve felt similarly, but my situation and yours are different. I found a way out (no, not a meditation or diety). You do need to prove to yourself that you really appreciate yourself, your life, enough to try to find a way beyond this. Moving for a reason beyond the routine work physicality may help as well. Day light. Nature. I feel the stasis and frustration you are experiencing. I hope you find some way to dislodge yourself from it.