Baby measuring small

Ma

I had my 24 week appointment today and the ultrasound tech said baby weighed 1 lb 6 oz. When I saw the doc he said baby was measuring small and that she wanted to see me back in 4 weeks to measure her again. Anyone have any stories similar? I'm kinda freaking out. He said baby is in the 20 percentile and they would be concerned if she went below the 5 percentile. But this pregnancy has given many mini freak outs. I had a subchronic hematoma at the beginning, I've got low platelets so that's kinda freaked me out not knowing what'll happen then, and now baby measuring small.