I think the standard way of diagnosing sjogrens at first is to give you a schirmer test where they put a special piece of paper in each eye to measure moisture, then it is followed up by a lip biopsy and bloodwork for ssa and ssb. I have been diagnosed with sjogrens by a schirmer test.
As for dryness, you don't always notice it, but once you take the medicine to create more saliva, like salagen or evoxac, you definitely notice a positive improvement. You have less tartar buildup on your teeth, swallowing pills is easier and your eyes are glassier. It is possible to not notice the dryness, but I would ask him to do a schirmer test if he hasn't already.
As for thirst, I've never heard of sjogrens causing excessive thirst, but diabetes and hashis can, if my synthroid is messed up (too high or low) I get water/sodium balance problems and it makes me thirsty. Medicines can cause excessive thirst and being out in the hot sun alot is really dehydrating and if your meds make you sensitive to the sun then you can get it worse, I get really thirsty. I had a problem where I was drinking almost two gallons of liquids a day and my urine was clear like water and my doc just told me to drink less. It was hard, because I was so thirsty, but once I did, the thirst went away. I guess its a viscious cycle sometimes. Also, she said drink gatorade, because the problem was electrolyte imbalance more than dehydration, so she said I was thirsty because I wasn't getting it quenched with what I was drinking, even plain water. I'm sure there's other stuff that causes real thirst and I'm sure someone else will post. My sugar was not elevated or low during these periods of excessive thirst and I never got a clear explanation of why my electrolytes keep going out of whack. I am on a diuretic (HCTZ). Also, it may be the hot sun thing and sun sensitivity. I hope that you get through this and be sure to keep in touch with the doc if it doesn't go away because one time, my bladder and all shut down and not only did I have excessive thirst, but I didn't urinate for three days and boy did that hurt and I had to go to the er and be catheterized, twice it happened. two other times I had to get ivs of electrolytes.
It's been a hot year where I live. Anyway, I hope this helps some and I hope you feel better soon. I know that thirst thing is the worst, its just awful. It seems the more you drink the worse it gets sometimes. Gatorade did make a difference for me and there is some sugar free stuff like that, fitness waters and all. Take care.
--Doctors are men who prescribe medicines of which they know little, to cure diseases of which they know less in human beings of whom they know nothing.--Voltaire (1694-1778)
Ills--Sjogrens-Lupus-like AI Disease, Hashis, Vitiligo, spinal stenosis/fusion with plate, salivary/lymphectomies, Diabetes, NAFLD, COPD, RLS, neuropathy, trigonitis, hystero, diffuse brain atrophy
Meds--Plaquenil, Evoxac, Metformin, Synthroid, HCTZ, Estradiol patch, Prosed, Klonopin, Soma, Ultram, Vicodin, Restasis, Albuterol,steroid injections, Protopic & Triamcinolone Acetonide ointments