Elizabeth, I had diet-controlled GD with my second baby. I also kept an eye on my blood sugar afterwards and while my post-meal figures were fine, my fasting was also elevated. It hovered in the high 5s and then one day it was 6.1.
That was the first day of my new life. I started an exercise regime that I grew to love, and I binned most carbs. I went on to cut sugar out completely. I spoke to doctors about it all. I have lost four stone, my insulin response is still normal and my fasting levels are lower, although still around 5, which I would like to see go further down.
My year-on post-baby hba1c test was 5.1, which my GP was very happy with (I would have preferred to be a bit lower though). I now eat and move completely differently and, while I know my chances of Type II are higher than if none of this had happened, I have done everything I can to minimise them.
So you can do the same. Go and talk to your GP, although be warned that there are plenty of old-fashioned ones out there who will say any fasting blood sugar under 7 is completely normal. See if you have a slightly more progressive one! Ask for an hba1c - this is now the standard diagnostic for diabetes. I think I have dawn phenomenon, in which my liver dumps sugar into my blood stream in the early hours causing a higher fasting level. It's a pain, but my blood sugar is pretty normal the rest of the time so I try not to fret. Your fasting levels are NOT diabetic, but anything over 5 is considered on the high side by many diabetic experts, and over 6 is often described as pre-diabetic (a pretty disputed term, but an indicator that something is wrong).
Remember that one thing the medical profession seems pretty united on is that most of us can do quite a bit to prevent or delay the onset of Type II diabetes. Good luck with it all. And as mygrandchildren says, it's not the end of the world if it does happen.