Due date issues?

Have any of you been told your due date is a certain day based off an ultra sound, but you know the day you got your period and the day you conceived, so you know your due date is a different date? My OB/GYN says I am either 12 weeks or 14 weeks. Considering this isn't my first pregnancy, and I know the exact date I conceived, I am fairly confident I am 14 weeks. Should I just wait until my 20 week ultra sound to be sure?

Early US are more correct then later. My due date was off from my LMP because I ovulated late.

Oh, I did not know that. That makes sense, I suppose.

This is happening to me. But mine is only by a couple days. But i still wouldn't of been able to get a bfp when i did if i went by their dd.

But an early us is supposed to be better than a later one BUT they r remeasueing me at my big us.