Tara i wouldnt stress to much about what they say. They cant see whats going on inside so how do they know accurately whats bub and whats placenta, fluid, blood and any other good stuff i left out.
Babys dont necessarily get bigger either as my first was 9pd 3 then my second was 7pd 12 and this one isnt going to be huge either. I think Dr's get enjoyment out of trying to scare mums and the size of their bubs.

Its the head you need to worry about not the size of the bub anyhow, thats the part that hurts the most. You will be fine .