Sooooo based off of my last first day of my menstrual period my due date is supposed to be Dec 13th my last menstrual period was on March 8th, when I went to the emergency room they did an ultrasound and the doctor went based off of what the embryo looked like and she told me my due date would be Dec 20th and that I was 5 weeks and 3 days... if I put that in the apps I get that my last menstrual cycle was on the 13th but it wasn't. if i go off of what the doctor told me I would be 7 weeks and 5 days but if I go off of my last menstrueal cycle i would be 8 weeks and 5 days.... which one do you ladies think I should go off of?