Not 6 weeks ??

Okay girls I'm beyond confused lol

Based off my LMP I would be 6weeks exactly today, well I went in for a ultrasound and as soon and the want went in I was in shock it was there ... But couldn't see baby?

The tech lady said I was measuring more like 4weeks and some odd days! But that can't be right ... I even went into my apps and seen I ovulated 20th of August, and I've read it can take up to two days later to actually conceive so if I go by that id still be 5weeks 5 days ..

If I put in I conceived literally August 31st it then says 4 weeks 3 days like the tech said, but i don't see how that's possible as I had symptoms for two weeks prior to that date and got s hard positive 4 days after the 31st ... Said I should have been measuring around 0.01 but i was only measuring 0.83 none of this makes sense to me !!!

Please give me your thoughts ! I go back October 8th.