My dr changed my due date

I missed my period September 10 that’s when I took a pregnancy test. I would have ovulated the week of Aug 20th. Which means I found out at 3 weeks pregnant.

The thing is my due date was May 12 and he pushed it to May 23rd. My instincts tell me I’m right for may 12.

Oh he pushed it back because the baby was measuring two weeks behind

Anyone else find out a three weeks? I feel like I should ask for another scan later on for growth and make sure the baby isn’t just small. 🤷🏻‍♀️