Understanding GD

I live in the UK and use a blood sugar monitor is called AgaMatrix. My goals from my midwife were to have results below 5.3 in the morning before food and below 7.8 one hour after a meal.

I’ve been getting results of 7.1 of which I’ve been feeling extremely tired, lightheaded, headache, nauseous, even though it’s still under 7.8 and I have only eaten what’s in my meal plan from my midwife/nutritionist.

I don’t understand. Why the results are getting so high when I’m eating what I’ve been told to eat, and why I’m getting those symptoms when it’s under the 7.8.

I was told it can be controlled by diet and exercise?!