Counting from my LMP my due date was 15 July.

But when I had my first scan the baby measured 6 days earlier giving me a due date of 21 July. So my dates went backwards! The OB keeps both dates on his records but we (myself and the OB/midwife) go by the scan measurements which means I'm 16w today instead of being 16w6d.

It sucked going backwards a bit! But nevermind. You forget about it after a while!

It's all just an estimate anyway. The baby could come 2 weeks either side of the date.