confused about how many weeks I am

Ashley

I went to an ultrasound and according to how I was measuring then I should be 25 weeks 2 days which makes my due date November 4th. however, my OB said that my new ultrasound is looking like I'm due November 8th. does this change how many weeks I am? I've been tracking my weeks on a app so I just want to make sure I am at the right weeks.