@condorbirdy - The American Brain Foundation has some information on brain fog and possible causes that might be helpful to scan through - https://www.americanbrainfoundation.org/what-is-brain-fog/. Also the National Headache Foundation has some information on a condition that shares some of the symptoms you mentioned - Idiopathic Intracranial Hypertension (IIH): High-Pressure Headache:
https://headaches.org/resources/high-pressure-headache/
Are you still working with your doctor or specialist to see if there are other tests that should be considered?