Anatomy scan. Nervouse

So next Friday Oct.9 I have an anatomy scan and I'm sooooo nervouse. I'm not showing really that much I'm currently 17 weeks 4 days prego with my first. I'm a little on the chunky side and I'm tall. When I went in at 16 weeks for pre natal vist we heard the heart beat on a dopple and the doctor said everything is going good. I'm just worried that my baby is to small or isn't healthy. Idk if I'm just paranoid or if I'm just crazy. Ahhh!!