@ilnyarienà faire I'm in an almost identical situation as you, similar age / calories / issues / timeline, although I'm less depressed and more apathetic.
I think my issues were caused by frequent use of various antihistamines for my allergies, I've had moderate success with nicotine (8-12mg / day), avoiding antihistamines, as well as lymphatic drainage exercises, & low impact cardio.
I do frequently get white tongue, so endotoxin is a concern as well.
I also think it may be low estrogen, or low steroids in general, as a single drop of androsterone is enough to make me fatigued.
You may want to look into blood pressure and blood flow to the brain, I had a really good two weeks when focusing on those 2 things although I haven't been able to replicate since.
Was there any medication you were put on a few years ago, or specific supplement, or life event you feel may have started these issues?