Due date confusion

UPDATE:they some how had my ultra sound as 6/14 instead of 7/14 so my due date is feb 21st. Thank you everyone who tried to understand it with me! Ok here is my sotuation and I do not understand at all. Maybe someone can explain it differently or is experiencing the same thing? The first day of my last period was May 6th. I ovulated around May 28-30th. Glow predicted February 16th. When I saw my dr at what we thought was 9 weeks. They predicted February 10th. Ok... Not too far off from what I thought. They did an ultra sound and said the baby measured about 8w4d. My paper work all says 9 weeks and she changed my due date to January 21st.... I'm not sure I understand. I am calling Monday. But it's driving me crazy.