Look into multiple sclerosis or myasthenia gravis as possibilities. Try a different neurologist maybe at Mayo or a university hospital where they see more unusual cases. Note that my son and I both have a rare hereditary neuropathy that has caused ongoing weird issues like that for decades. Very slowly progressive. I was tested for suspected ALS, MS, MG and my son for CMT but we have extreme cases of HNPP. It’s very frustrating and challenging, impacts quality of life yet doesn’t stop us from living life. It will probably not shorten our lives. I share this to give you hope that it may not be anything life threatening. Lots of weird and unexplained neurological problems out there. Look for a neurologist who will at least listen to all your concerns. Prayers for you.