When a person has a varied list of inflammation symptoms, yet standard tests are normal and no doc has come up with a Dx over the course of years, that usually is an immune system dysfunction.
"Body feels like I have a flu without the fever"
That could be the malaise as in MCAS or CFS. MCAS is an emerging disease, but even the American College of Allergy, Asthma and Immunology now recognizes it: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6026564/#
"spaced out feeling"
It's called brain fog
"Symptoms usually start or get worse at night"
that's typical of inflammatory conditions
"Mother had neck surgery for neck arthritis and bone spurs"
I'd want her re-evaluated for Ankylosing Spondylitis, now renamed to axial SpondyloArthitis. There is recent thread here to read through. Note that there is even a version of SpA that doesn't involve spine or joints, called 'extra articular' - esp if you are female (which your profile says).
All 3 conditions named above, as well as many others, have a lot of overlap.
Food allergies can be suddenly onset and cause a Miriam of multisystem symptoms because of the autoimmune response. When it feels like your whole body is physically and mentally unfunctional, it could be a “non-ige” allergy. There is NO test other than elimination diet for 3 weeks of suspected allergen. The reactions are also delayed and symptoms from one exposure can last weeks. Make a food log, and try 3 weeks of an elimination of the 6 most common allergens. Dairy, soy, eggs, wheat, nuts, seafood. After 3 weeks add one back in at a time to see if symptoms return. Hope this helps!