Wa'alaikumassalam! Don't worry lah, 3.2kg at 38 weeks is actually normal range, babies grow differently, and with GDM diet control you're doing everything right, so the baby size is good sign lah. A few of my mum friends juga had GDM and their babies were similar weight, all turned out perfectly fine, so trust your doctor and yourself! Just make sure you rest well these last few weeks and follow your doctor's monitoring, usually they track things closely with GDM so you're in good hands. Mummy, you're doing great!