Doctor not happy with measurements?

31 weeks and went in today for my appointment and he ordered me an ultrasound because he said I’m not measuring as big as he’d like. Up until now there hasn’t been an issue. He said I’m petite so he doesn’t expect a big baby but just wants to make sure.

Anyone else get told this and everything was fine? Or anyone get told this and it not turn out fine?

Just semi worried ☹️