Everyone keeps saying I'm too small

I'm 35 weeks today, I have been measuring to the date every time I have had an appointment and they have checked my bump. I haven't had an ultrasound to check the little nugget since my 20 week anatomy scan and my next one is not until next week...

Throughout my pregnancy people would be surprised when I said how far along I was because my bump is small. I'm not a tiny framed person, I'm curvy. My starting weight was 150 at 5'4 and I'm at 172 now. Today at work in a meeting so many women were AGAIN telling me I didn't look 35 weeks. It's really been bothering me and now I'm so worried!! I'm worried that when I'm measuring correctly at the obgyn that it is just measuring the growth of my uterus and amniotic fluid and not my son. Is that totally false and out of control? I can't even bring myself to look it up.

Anyone else having this experience or has had it in the past? I know everyone carries differently but I'm so nervous tonight. Any feedback would be appreciated!!!!!