Unsure of due date


I've been to the Dr twice, the 1st was to confirm my pregnancy with a transvaginal ultrasound. 2nd appointment, I had another transvaginal ultrasound which was a better view of the baby. If I go by the 1st day of my last period i would technically be 10w3d. But the ultrasound is measuring at 9w2d. Now the Dr said that she isn't 100% sure which due date to give me because I'm right in the middle of the cut off date. So it's between December 27th - January 4th ... So if she's unsure then i definitely have no clue ... Has anyone else have been in the same boat?