To any other type ones who have already had children or have some kind of advice for how I'm feeling please respond!

I just entered the third trimester recently and all of a sudden I'm having problems keeping my blood sugar up?!? I thought that it was supposed to continue to get higher but all of a sudden my blood sugar isn't getting above 128 which is both good and bad.. It's meant a lot of lows including two extremes 31 and 37. It just started in the past couple days baby is measuring big (3 lbs 11oz at 28 weeks) which makes it seem like I would need more insulin not less, but all of a sudden my numbers are behaving like I'm not pregnant but I obviously am. I'm eating so much during all these random lows to the point where i have to force myself to eat at mealtimes. I don't have an appointment with the dietician/nurse until Monday and I don't know what I can do to prevent these lows.