Due date (dates)

Ka

So. Currently according to my OB and my 12 week ultrasound, I am 19 weeks and 1 day. I went to my anatomy scan and they had me at 18 weeks 4 days. I was confused and asked why they had it at that and they said based of your LMP. But the thing is, I didnt know that date because I had irregular periods. Once i told the tech that she got really snippy with me and said "just be quiet so i can do this ultrasound, take it up with your doctor" I said okay fine. Well after all the measurements and such were done my baby girls is measuring ahead at 19 weeks 3 days.

Well the doctor who looks at the ultrasound came in and pushed my due date back by 3 days. Which I dont get since shes measuring ahead? Does it really matter that much since all these differences are only a matter of a couple days? I'm so confused right now because I never had any of this trouble with my first twin pregnancy..

Every ultrasound ive had has given me a different due date. The 17th, 21st, 14th, 16th. So many different dates lol 😅😅