How far along am I really?!?

So I recently found out that I am pregnant and my family dr thinks I am around 10 weeks. I know that seems late to find out so let me explain.

My last period was August 27 and it was a normal period. Well in sept my period was late but I didn’t think anything of it because my periods are SUPER irregular. Well I got an ear infection and my family dr did a pregnancy test on Sept 27 in the evening and it was negative. Well oct came and went and I still didn’t have my period so I took a test last week and it was positive. So I went to my family dr and they did one as well and it came back positive too. She estimated that from my last period I would be 10 weeks.

My question is, if I’m 10 weeks wouldn’t it have shown up when I was at the dr on Sept 27?!?

I have an appointment with my OB on Wednesday.

What do you ladies think?