What causes weakness moreso after walking through the store, driving?

[Pasteltulips2882]

Hello,
7 years ago it started out with arm weakness that mostly occurred after cleaning or lifting. A year later my right side became weak. 3 years later all 4 limbs suffer from mild weakness when I rest and really severe weakness after just walking through the grocery store. After coming home from just one grocery trip, I am severely fatigued, then a hour later my legs and arms get so stiff and ache. Then the hallway feels like its 5 miles away because my walking is so weakened. Now after resting a few days after one trip my legs and arms will still be left weak but will get enough strength to be somewhat normal. On days i have lots to do, the severe weakness can last up to 4 weeks. I have had eegs, emgs, Mris, and blood work. Results are 1 spot on frontal part of brain found 2 years ago. Severe low blood platelets for 3 years straight, celiac disease, heart arythmia, and thats basically it. I am 37 lead a stress free life with meditation and yoga when i can. Anyway I suffer severe fatigue, my symptoms are worse with illness, flu shots, and any exercise. I have a family history of MS, and Mitochondrial Disease all on my mothers side as well as lupus which I dont have and alzheimers. I had a upper back and neck MRI done as well only showed degeneration of my neck bones arthritis. But have no arthritis anywhere else. I take vitamins eat healthy but also low on Vitamin D. Any suggestions for tests the doctors could test for would be appreciated for this is my 5th neurologist. My current neurologist is starting over from the beginning. The other doctors were new in practice and said it was stress related. I know stress is damaging but I saw a therapist who tested me and said I was good. She told me to keep trying and find out what is truly causing these symptoms. Honestly though my marriage and family life is so loving and no history of abuse etc. So what can cause weakness, fatigue, cold intolerance, when just driving longer than 10 min or walking longer than 10 min? I used to run 2 miles a day before this hit me and I want to be able to get back to biking, hiking, and not having to use a motor cart in the grocery store especially if its something that can be fixed. Thanks