Dear XXXX
from the multipe negative HIV tests you did, it seems obvious to me that there is absolutely no evidence for HIV infection. So HIV is nothing, I would be concerned about at the moment.
I understand that you suffer from some kind of inflammation of the salivary gland,
but I do not think that this is related to an active virus infection.
However, from the information you gave me it actually seems possible that some (per se harmless) viral infection you acquired earlier (some years ago), triggered an autoimmune mechansim,
that now causes the symptoms of xerostomia and sicca syndrome.
However, in such a case the triggering virus would be long gone now, and it could no longer be detected and especially not clearly related to the symptoms you describe.
So, from a virologists point of view, for your actual problem there is no additionally virological diagnostics that come to my mind.
I hope that helps you.
When you have further questions, you can call me (Tel.: XXXXXX), since it is faster to give advice via the phone than writing everything down.
Yours,
XXXXXXXXXXXX