I remember being cold and wrapping up in blankets and staying near the woodstove in December. My nose got cold a lot, it seems like that was the first thing I really noticed and at night I slept with extra blankets. My guess is my calorie intake wasn't high enough. The body needs fuel (like my woodstove) and you probably had a dependence on glucose for internal heat generation. When I switched to LC my muscle cells didn't have enough of the required enzymes to break fat into ATP for energy. As a result I took in more glucose/carbs and took the process slower. Weight and BG came down pretty fast and, besides the cold, I felt like my system was out of whack, that something was very wrong. So I stopped trying to lose weight and stayed at the same weight for about a year. I was careful about what I ate and kept my blood sugar in an acceptable range. The main thing was to be healthy. Recently I've changed my regimen and am dropping weight again to get to an ideal BMI.
So to summarize: your body may be used to burning glucose but it needs to change over to fat burning and that will take time to build up the right enzymes.
In regards to your other question "How long have I been diabetic?" My definition of diabetic is more stringent and based on insulin resistance and not glucose levels. Therefore my guess is this problem has been developing for the last 10 years until it was bad enough to be acknowledged by doctors.
If you stay on your present course everything will work out well and you won't have any diabetic complications.