Measuring smaller than I thought

I went in for an ultrasound a few days ago and they took three measurements. 9 weeks, 8 weeks 5 days, and 7 weeks 6 days. They averaged that at 8 weeks 4 days and told me that’s what I was when I left. However, according to the first day of my LMP (September 10) I should’ve been like 10 weeks 3 days today. Basically, I’m 9 days behind. I’m almost positive I didn’t ovulate late because my periods have been pretty regular, averaging 26 days. I ovulate around days 12-14 of the cycle. I had sex September 22 and September 26th. Took a pregnancy test October 14th and it was positive. I obviously don’t know the exact date of ovulation. I’m assuming it was like September 30 or October 1 based on the measurement but I’ve heard because my abdominal ultrasound was so early, it’s really not that accurate. My next one is 11/29 and I’ll be about 10 weeks 3 days then. I’m hoping they’ll be able to scan more clearly? This time, I’ll have a full bladder and be doing it at the hospital instead of a private office. From what I’ve read online, some women just measure smaller than others. Any advice on this? I’m kind of obsessing and stressing over it.