Dear B12,
Last night I gave some further thoughts to my original reply to your unusual 'diabetic' problems and spent some time going through my own diabetic notes to see if I could possibly find an answer. Obviously not being medically qualified I would never attempt to make any diagnosis, but I did find in my diabetic notes something which matches most of your unusual symptoms.
It's only a guess on my part, but you may well be suffering from a condition known as 'Diabetes Insipidus' which is not diabetes as 'we diabetics' have come to know it in the conventional sence, but is the end result of a hormonal imbalance within the body. I should point out that this type of diabetes is very rare, yet it still gives the sufferer many of the classic symptoms of diabetes, frequent use of the toilet, dryness in the mouth, erratic B/G control, with No Glucose being detected in the urine, and a HbA1c reading that is more often than not relatively normal.
This type of diabetes is caused by problems that are associated with the Pituitary Gland and is easily detectable in the same blood/test that I suggested that you undertake to have your Thyroid function checked in my previous reply. Because this type of diabetes is very rare it is frequently miss-diagnosed. Fortunately it's usually easily treatable once its been clearly established, so don't delay and 'badger' your Dr for the appropriate blood tests.
Please let us know how you get on - Best Regards - Lazybones