I disagree with some of what your doctor said about testing in regards to Sjogren's...because I have personal knowledge that patients can be entirely sero-negative (including ANA panel) and still have a positive lip biopsy confirming the diagnosis. But this is not uncommon for doctors outside of the rheumatological field to misunderstand autoimmune disease.

Your findings are confusing in some ways...being that nothing shows, even on skin biopsy, BUT there are many causes of PN so I wouldn't discount PN as the culprit. You do seem to have some anxiety over this and that alone may be exasperating your symptoms to some degree, but I doubt it's the 'cause' of the problem as a whole.