Try going on a strict low carb diet like paleo or atkins, drink plenty of water, and work out a minimum of 30 minutes a day. Then monitor how your body reacts and make sure to test your sugar in fasted state (morning on an empty stomach), and 2 hrs after each meal.
I was diagnosed pre-pregnancy and after going paleo and working out, I am off all meds and my sugar readings are in the lower spectrum of normal non-diabetic range. I prefer paleo over atkins because it stresses the importance of eating clean, organic, hormone free, minimally processed foods.
Ask your doctor if you can try this for two weeks, just remember it's a commitment, but will be worth it for your baby.
Good luck, I wish you the best!