Due Date Changes

Hi moms, I need opinions.. I've only seen my OB twice since I found out I was pregnant he did an u/s of course to confirm pregnancy..He gave me a due date of 12/27, which would make me 15 weeks & 2 days...I haven't had any testing done..June 30th I visited a nonprofit organization that helps mothers get in programs while pregnant..The nurse at the facility did a pregnancy test to confirm pregnancy and she did an u/s as well... She told me my estimated Due Date was 12/19 which would make me 16 weeks & 2 days...I was able to find out the gender of my baby which is a boy 💙...Should I go by her due date or my OB?? I'm very confused !