Personally I only trust FRER's so I would be wanting a bfn on those before I was satisfied. I'm not 100% sure but I don't think there clear blue digital tests are as sensitive as the FRER. In saying that though if it is a longer cycle it is unlikely conception would have occurred but you may have had a late implantation as well. Unless you get a blood test I don't think you can truly be sure it's a bfn until AF arrives