Who had a small belly and a small baby? I'm 37 weeks 1 day, doctors sa…

Who had a small belly and a small baby? I'm 37 weeks 1 day, doctors say in unison that my belly is small, meaning something is wrong with the baby. Sent for an ultrasound. And indeed the baby corresponds to 35 weeks, but they told us everything is within the norm, no pathologies. Now, how do we count the due date? Should we stick to the first ultrasound or now? After all, there's a 2 week difference. Or should we rely on the due date from the first ultrasound, but the small weight will be?