Several things stand out in your story. Did you have a Covid test done with the bad cold in Jan? Covid infection can trigger autoimmune disorders. One that fits with your symptoms is CIDP mentioned earlier. It affects the nerves primarily and muscles secondarily. Your positive ANA should not be disregarded considering your symptoms! It shows a potential link to AI diseases and should be repeated and explored further. A better test than the standard tests is the Avise CTD (connective tissue disease) blood test. I would ask rheumatologist for that. Myositis is also a possibility, an inflammatory disease of the muscles. Muscle enzymes should be measured in blood (CK, ALDOLASE,ALT, AST, LDH) and if any are elevated a myositis panel should be run.
The good news is that MS and lumbar disc disease has been ruled out. The elimination process is helpful at getting to an answer. There are special Drs that are neuromuscular docs and that’s who you need. The university or special clinic systems recommended by others is your best bet to find one. In the meantime do keep up with PT, as it will preserve the function you have and help improve it. I would leave no stone unturned in getting a diagnosis as early intervention is key to prognosis and recovery! Good luck and keep us posted please!