I have Sjodrens with a positive blood test but I don't really have dry mouth or eyes, so don't let that convince you you don't have it.
You have one autoimmune disorder so are likely to have more as they like to travel in groups.
Check out Hughes Syndrome Foundation, we have a support group on health unlocked.
I know you say it's not thyroid and will know loads about it, but have the docs checked for thyroid antibodies, and T3 and T4 ( I think). Check out Thyroid UK
I Hughes Syndrome or APS which can cause PN. I do get burning feet, sometimes on the tops of my feet, for no reason. And very painful fingers but after a lifetime of ill health I tended to think its just tough as I am on warfarin and failed on plaquenil only steroids left.