Autoimmune diseases are very hard to diagnosis in some people. My bloodwork comes back positive for autoimmune disease but when the specialist does further testing and everything is negative! I have been battling this for years. Like you I recently had Covid and all my symptoms intensified, If you have access to labs online be your own
advocate find out what blood work they have ran. Look for an ANA and what you level is. Hopefully they ran a C-Reactive Protein. Find new Drs if you have to. Also for me I can say that following a anti-inflammatory/ low fodmap diet has also helped.