Two different due dates... frustrated

I guess I’m just venting! My first ultrasound the tech gave me the due date of Dec 9th, which I thought was a bit off because I know my LMP/ovulation etc., but okay fine, I may have ovulated later than I thought or something. I then had a second ultrasound done at (what I assumed) was a little over 11 weeks pregnant and the tech told me I was actually measuring about 13 weeks and my new due date is November 29th. Well NOW I’m at my doctors office and he’s talking my due date still being at December 9th. Like which one is it! I would really like to know. He said it would be confirmed at my anatomy scan but that isn’t all the way until the end of July. So I don’t even know what weeks/ dates to go by anymore. What do you girls think 😩