recommendations...

which test do you all recommend I use? I have tested with .88 Wal-Mart cheapie, frer, clear blue, EPT, and off brand blue dyes. all lines are still super faint on all of them. I am now officially 12-13 DPO. I'm due for AF on Sunday. I really want to test but I want to wait too, but it's so hard. when will my lines darken?