I know it is so easy to get in a tail spin about these things in pregnancy but for clarity i will summarize your post for you.....
You have been screened twice for GD and both screenings have concluded that you do NOT have GD.
Your GP is not up to date with current GD guidelines.
You have had extra screening and it showed a perfect and healthy baby.
Your normal lifestyle is active and healthy with most things in moderation.
Honestly when you break it down like this I think it becomes clear. You do not need your doctors permission to stop testing your BSL or to return to a normal healthy diet. It is your body. If it was me I would completely move on, confident in the knowledge that I do not have GD and that my baby is well. If you feel uneasy about this then I would ask your GP to refer you to someone to discuss it further (OB or diabetic educator) and I would completely stop discussing this GD issue with the GP.
Good luck. X