Curious about something! Due date changes

My entire pregnancy with my son, I only had my due date changed by 1 or 2 days each time so I wasn’t concerned about how far along I actually was, every doctor always went by the original due date. This time baby is measuring small, I’m supposed to be 21 weeks Monday but I can picture them changing my due date because of the discrepancy. Has anyone ever had their due date moved by a week or more and still went by your original or how did you consider how far along you were? If they change mine it’ll be May 16th to May 24th, so 8 days difference. Which would definitely have me at not 21 weeks Monday 😂 just curious if anyone else has been through this stuff too :)