I agree with John all the way. After 50 years of Type 1, I am fairly unaware of low glucose levels, so I have to test constantly. I can function just fine at 40 one day and be completely out of it and in need of medical attention the next.
Additionally, over time a lot of low levels will affect other things, like brain and heart. It is hard to run perfect numbers, but I would guess something has changed in your life and it could be as small as the weather. Readjust a bit and see if you don't feel better also!