This is going to sound dumb. But my last full blown period was September 24th. I ovulated on October 11th . I don't get why they want you to calculate your weeks pregnant based off your last period and not your ovulation. I'm scared to think I'm further along then I really am!
You are supposed to calculate 38 weeks from when you ovulated if you are sure that's the day you ovulated. Like pp said, you can only know if you were tracking bbt.
Even if you know lmp and when you ovulated, you will probably get a "new" due date when you get your first ultrasound, where specific measurements to determine how far along you are.
Re: Question