I go for my confirmation blood test in the morning. I have irregular cycles so when do they generally date the pregnancy? I am curious to pin ponit how far along I am.

~ Diagnosed with PCOS in March 2009. Taking Metfomin for insulin resistance and irregular cycles/ovulation.
Had healthy baby girl in Jan 2010 via C-Section (HTN and Breech Presentation).
~ Miscarry at 8 weeks with D&C in May 2011 (low progesterone).
~ Had a healthy baby girl in June 2012 via C-Section (on prometrium to sustain).
~ Surprise pregnancy at age 40! Baby boy due April 26, 2021 (took prometrium to sustain once pregnancy was confirmed, 3rd C-Section planned).
Re: When do they date?
It was confirmed at my first appointment and I was 6 weeks along.
I have irregular cycles, too, so at my first appointment last week (at ~5w4d), my doctor ordered an early ultrasound for me, to confirm the dates. I go in for it this Thursday!
So I think it varies by practice, but it would be worth asking your doctor about getting an early ultrasound. My OB felt it was important to firm up the EDD, in order to plan checkups/tests/scans appropriately.