Measuring small

I'm 39w1d and at my doctors appt yday I was told I'm measuring 35w. Does that automatically mean my baby is gonna be small? Idk if that sounds dumb or not. I've gained 20lb so far and I'm due on Monday. Everyone tells me she's gonna be small but then there's that one person that's like "she's gonna end up being big as hell". Obviously I won't know til she's here but I'm curious if anybody has had surprisingly big babies. My doc hasn't mentioned a single thing about how much she would weigh at this point.