I was reading through your post and back a few pages I wished I could interject about your scan, as soon as I saw you were booked for the 29th the first thing I thought is you probably won't see anything which is awful when you're already suffering bad anxiety!
2 years ago I got a bfp, around 12dpo, but wasn't tracking. Like you I used FRER to follow progression, and around 13/15dpo I got a few lighter tests that sent me into meltdown! I was a blubbering mess, and continually googling, I was booked in for a scan 3 days later which we saw nothing, no sac, (a possible shadow they said) me levels were around 800 by now when we didn't see anything. After a LONGG 3 day wait they had me back for another scan, we saw a sac & fetal pole! then a week later HB! but my levels were at 10,800 before we saw this! the doctors were sure I was ectopic because of high levels and nothing showing on scans. They were even talking about key hole surgery to investigate.
so what I'm trying to say is - those tests are unreliable, as long as the vast majority are getting darker try not to worry (although I know its impossible) I think indicator of a problem your test would consistently be getting lighter, the only thing consistent about yours is the fact they're getting darker! and please don't worry about your scan, My lg is now 14 months, I couldnted back from her due date, and worked out at my first scan I was 5w 3d when we didn't see anything, 5w 6d when we saw the fetal pole, and 7+ weeks when we saw HB! Sending all my love to you x
P.s have just had a scan xmas eve I'm estimated around 6w 1d at that point, and it was ridiculously tiny, I think if we went a few days before we wouldn't have seen much, if anything xx
(pic of my tests getting fainter)