Welcome, Dura! :welcome:
Insulin should bring your glucose levels down pretty quickly. You may need to get with your doc and tweak doses, especially at first, for best effect. (I was able to get tweakage advice via phone and email ... but I had to be the one to start the conversation).
As for feeling better ... if you've had high levels for some time, lower levels may feel weird at first. In addition, starting low-carb can bring on a case of "Atkins flu," which is just your system getting readjusted. This "flu" can last anywhere from 3-10 days, give or take.
It took me a few weeks to feel anywhere near normal, most of the time. But even during that phase, I felt healthier than I'd been in a very long time.