Doctor says I'm hiding the baby -measurements

Amberrrr

I just had my fetal growth ultrasound this morning. According to the US, the baby is 5 pounds. He's perfectly healthy and everything. But Doc says I'm measuring small. I've measured small before. Is it strange that the baby is measuring right on track but I'M not? He wasn't concerned, and i'm not really that concerned either. He said I'm small, and hiding the baby. I told him I sure don't feel like it, lol. But just out of curiosity, and maybe some boredom, have any of you experienced this as well?