Your dry eye (xerophthalmia) and dry mouth (xerostomia) symptoms-
my Greek and Medical terminology background help!- are typical symptoms of Sjögren's syndrome, which can be diagnosed by a Rheumatologist, but it is not an easy nor a fast diagnosis by any means.
It usually requires a number of tests, medical history,clinical examinations and ... a lot of patience!
You need to rule out oral Candidiasis and Candida (yeast infection) in general, as well as STDs, specially, if having sex with different people, which increases your risks.
Any excessive alcohol consumption, improper diet high in sugars & starches , antibiotic treatments, stress etc. are contributing factors in fungal/yeast infections.
Hope this helps, however, my suggestions are not to be considered as substitute to medical advice.