Worried!!!

Okay I had my hands on appointment today and they looked at my anatomy scan. Buggys measuring small and she's not super concerned but there is still concern there. She said he's not an unhealthy small. I'm just absolutely worried and terrified if he doesn't get as big as he needs to by September. Any advice to calm the ftm down or how to possibly get buggy to help him grow. (Currently 20w & 5d)