I started seeing a new doctor about 3 weeks after my last appointment with my old doctor, this new doctor thinks I’m measuring small and has been thinking that the last 2 times I’ve seen her. (3 weeks off to be exact)

I’m going in for an ultrasound to take a better look but I was just wondering if they can actually tell the baby is small from just measuring my belly? Could it be that my body frame is just not expanding to what she expected? I had a smaller body frame before getting pregnant and I can’t help but feel like that’s why I’m measuring small, since the baby was looking very healthy before this.