THIS. From watching my husband deal with diabetes I'd agree that the body becomes accustomed to high sugar levels. He had high blood sugar for years (his A1C was, not atypically, 9 or close to 10). Then he participated in a drug study ... and his A1C began to plummet. (It's now at 5.6) At first, he felt AWFUL: his brain got fuzzy, hypoglycemic-type sensations, etc. It took him a good six-eight months for his body (specifically his liver, I think he said) to get used to lower sugar levels. Once he adjusted, though, he began feeling like a normal human being again.

My personal theory is that the longer your numbers are high, the harder it is for your body to adjust to normal-range numbers, so it takes longer. As with all things diabetic, your mileage may vary, but I think you're gonna be okay given time. Hang in there.