My doctor and US technician don't agree on how far along I am.

I know that by all standards, doctors have a better understanding on the body and all medical aspects in general, but I can't help but trust the US tech as she was a) seemed very knowledgeable b) had confidence in her readings and c) gave me an expected margin of error for roughly 3 days on either side of the growth rate. My last scan (according to the US tech) says I was 7wks 3days (currently ~9wks) but my doctor went ahead and said I was about 6 days less yet he didn't see the scan or the measurements. I want to go off the US tech's readings but my doctor seemed pretty adamant 🤔 I'm. So. Confused.

EDIT: I haven't met with a proper doctor yet, just been seeing my GP (two of them) and my US tech who changes every time I go in. Xx