Baby measuring small

Morgan

This is my first pregnancy. Yesterday, I went in for our first ultrasound sound and based off of my last period I should be 7 weeks and 4 days. The Doc said my baby is measuring around 6 weeks and is very concerned. I have to go back for another ultrasound next week to see if the baby is growing. If it isn’t, it does not look good. Has this happened to anyone else when their baby should be further along but ends up growing like it’s supposed to? Thanks!