Baby measuring behind

So we found out Friday that our newest addition will be our fifth little girl 💓! I was supposed to have my anatomy scan Friday but the technician said she wasn’t going to continue with the ultrasound because my baby is measuring at 17 weeks instead of 20 weeks. I have a bicornuate uterus which means my baby has half the size to grown and move around in. My first daughter was only 5lbs at birth so I figure this baby will be small too. But the tech was kinda rude and worried me a little when she stopped the scan. I’m worried something is wrong with my baby.