Brain fog is common with autoimmune disease, but mine worsened significantly after I had Covid. My rheumatologist asked me to see a neurologist who did a brain MRI just to make sure there was nothing else going on. Perhaps that might be a good idea for you too. Cavities are linked to dry mouth and are common with Sjogrens. I get dry mouth from one of my other meds and my doctor recommended I stop drinking alcohol and coffee, and he suggested a product called Biotene (it comes as a mouth spray or lozenge). Best of luck with your upcoming appointment.