Should I be concerned?

Af was due on 8/12 and still no signs of starting. I've tested every other day since ( in the morning everytime ) and each time the test comes up negative. I'm very regular and I've never had to change my date on glow. I'm just so confused at this point. I've not made any changes in routine and during ovulation we only did the bd 2 times so I wasn't expecting it to be positive anyway but I'm confused at why I haven't started yet, is something wrong with me? Thoughts and baby dust please :)