Hi!
If you were my patient, I would advise you that ultrasounds done in the first trimester (transvaginal ultrasounds) are accurate within 5-7 days.
SO, the ultrasounds could be off by as much as one week, but probably not by two. If you were my patient, however, I would still recommend a DNA test as your dates are really too close for comfort.
Good luck!
Dr B
No. Ultrasounds are more accurate than dates. No way to know without a paternity test