Hi i am 26 wks and all mu ultrasounds have the same edd of 9/13 could it be off a few days or is it accurate to say i conceived on 12/22?

Yes, can be off few: The earlier the first dating sonogram was, the more accurate the due date will be. A sonogram at 6-11 weeks is ideal for accurately measuring the fetus which gives you the due date. Having said that, you can still be off by up to 7 days.

+/- a week or so: Ultrasound due dates are not precise. How accurate they are depends on how early the first U/S was done. An ultrasound at 8 weeks, for example, can be off by up to 5 days. An ultrasound at 12 weeks, may be off by a week. An ultrasound in the second trimester can be off by 2 weeks. Since the conception date is calculated from the ultrasound date, it could be off by the same number of days.