Just worried....

My doctor put an ultrasound in for me with AFI/EFW (amniotic fluid index/ estimated fetal weight) im measuring almost 4 weeks ahead right now. Im 30.5 today yesterday my stomach was passed 34 cm. At 27 my baby was measuring in an ultrasound at 29.5. She said she needs to monitor how big he is getting. I’m just worried about him ☹️ I’m worried he doesn’t have enough room or he will run out of fluid. I’m worried about preterm labor and not really knowing when he will come. Just needed to vent....