Thank you all, I'm heartened by the fact that she was pretty rushed and she wasn't really trying to date the pregnancy, just check on it. Also, I was told I was 4 days behind on the 3rd January, then on the 9th January I was told I was only one day behind, now on the 19th I'm back to four days behind apparently...seems like it can jump around. Fingers crossed for my 12 week, nearly 4 weeks away! But hopefully I'll have the Doppler in the meantime to help reassure me.
To doodle: I didn't think I was ovulating at all, but generally my cycles are very regular and I think I ovulate around cd14. By the looks of it, it may have been cd15 when I last ovulated, but it couldn't really be any later (despite what the scans keep saying) because I had a BFP 8 days later. I have to say that your post the other day sounded similar to my 6 week scan. I understand that sometimes it's kinder on yourself to abandon hope rather than cling to it, but to me it doesn't sound as if all is lost for you. Got my fingers really tightly crossed for your little bean.