Percentile (nervous)

I’m very nervous everytime lately I’ve been going to the doctors they mention my weight gain but fail to realize I lost 20 pound first trimester I finally gain that back and like 3 pounds I’m 33 wks my baby is measuring in the 26th percentile as of me being 31 wks. I go back in 2wks for another ultrasound I’m just trying to keep my head up