Nann do you know the sensitivity of those tests? It was 2xblue in dec 2ww I was thinking of. She had 25mui tests and started getting the faintest of lines at around 12-14dpo. At 16/17 dpo still faint but getting darker. She's currently in the ddg :) So it is still possible for your bfp. With af due Saturday you should surely have answers soon I hope. I can remember how frustrating it was for 2xblue when af didn't arrive but her tests weren't confirming bfp either...
519b48 Ovulation charts on FertilityFriend.com