hey don't worry the same thing happened to me. I was having a scan at what I thought was 8 weeks and then I found out I was only 5 weeks!! I was quite depressed about having to backtrack three weeks because I would've been 11 weeks pregnant but now I'm back to the 8 week mark. I'm just hoping the baby comes early because originally by my LMP it was supposed to be due Sept 1st and my best friend's wedding is Sept 13th but the baby is now due Sept 19th!! Yikes!! I'm using my LMP date though for when I take the time off work hahaha. Well I figured that they could be wrong, my bub could just be smaller and I'd prefer to be prepared than to be at work with my waters breaking!!