Should I change my dates?

I know this question sounds silly, since the dating scan is typically when they officially decide your due date...

But I'm 100% positive of my ovulation AND implantation dates, and if they were 6 days off (like my ultrasound says) then it would've been impossible to get a positive test on the day that I did. Anyways... my original dates give me a due date of November 22nd and after my dating scan my midwife gave me a due date of November 28th. I've read that some babies will measure small and then catch up to original dates by 12-20 weeks, so I'm unsure if I should change my dates or not, or just consider both for a while?