BlueMoon - how are you doing? What's the latest?
I'm in a similar situation and really regret testing. I'm feeling really scared and sad. Here is how my HPTs have gone:
Feb 21 (12DPO) - first squinter on wondfo
Feb 22 (13DPO) - similar squinter on wondfo
Feb 23 (14DPO) - clear line on FRER (the pic I'd posted)
Feb 24 (15DPO) - stronger line on wondfo than before (but still not close to control)
Feb 25 (16DPO) - [no testing]
Feb 26 (17DPO) - [no testing]
Feb 27 (18DPO) - line on wondfo is stronger than at 13DPO but definitely fainter than 15DPO
AF was due last Sunday (Feb 21).
I've been trying to explain it away but I really don't think I can. I used FMU all times. I guess it's possible it's because I've been drinking lots of water lately because of the kidney stuff and have gotten much better into the habit of drinking loads than I had been earlier on this week, but I thought that it doesn't matter as long as I don't drink much during the night before FMU. Having said that, sometimes a lot of pee just comes even when I stopped drinking water many hours ago. In any case, I think it's a stretch. And I know people say "a line is a line" and that all these sticks have different levels of dye and are not supposed to be quantitative tests, but I just don't buy it when I've seen so many people's wondfo lines reliably darken across time despite all that and I've heard of so many MCs when lines didn't darken or got fainter. And I've only seen a few cases on these forums of such light lines at 18DPO.
I wanted to take my final wondfo with more pee but it was an even shorter hold and I would've just been more upset if faint. I'll probably go and get another FRER today and test with FMU and try to not drink much in the evening (even though I should be drinking lots), but I've pretty much resigned myself to having a CP. I really wish I hadn't tested
ETA: My pee this morning was a very pale yellow, as it has been for the past few days presumably because I've been drinking lots. I don't know when it was, but I do remember having very yellow urine at some points that I've tested over the past week, but now I feel like I'm just clutching at straws.