Baby’s measuring small !?

I had a follow up today and my OB said my baby is measuring small but she’s not on the “abnormal side however I’m to go back now every 2 weeks u til my due date and they said they will also be monitoring her weight hoping she gets bigger, if she does not get bigger there is concern. I’m trying not to worry. I’ve had two losses and this is the farthest I’ve come in pregnancy. I’m almost 28 weeks and last ultrasound I had was for my anatomy scan. They are booking me an ultrasound to look at things.