Due date confusion?

Stephanie • Wife. Teacher. Mom to three boys 💙💙💙.

According to the app and my first day LMP my due date should be August 29. However I tested every day from my missed period and didn’t get a positive until my period was 10 days late, so I think I ovulated later in my cycle. Does that mean my due date would actually be into September? Or is first day LMP still the most accurate? I see people are getting their first ultrasounds and the doctors stick with the period dating rather than the way the baby is measuring. Any advice would be great!