Uy, I can feel your worry through the screen, mama, and it's so valid, pero this is really one para sa your OB, hindi lang ako! Since you're at 36 weeks with concerns about baby's size and growth, your doctor needs to be the one guiding you through this (they're already doing ultrasounds, which is perfect).
Hyperthyroidism during pregnancy is manageable, and the fact na normal na ang levels mo last month is already a good sign, pero only your OB and endocrinologist can tell you if baby's size is within safe range for your situation, especially with the sugar monitoring too. Keep those appointments close, and if you start feeling really anxious or anything feels off, don't hesitate to reach out to them sooner, Hindi ka nag-iisa dito, promise!