AF late, BFN!

Nicole
Okay ladies I'm hoping someone can give me some input.
I am on CD 38 (normally 28-30) my period is like clockwork. It has never been late in almost ten years! 
My chart says 21 dpo. However, my opk wasn't completely clear. It was equal to the control, but not darker. 
I have read people getting the bfps really late after a missed period but I don't want to get my hopes up.
TTC #1 since August 2013 and never had a late period. 
Any advice is greatly appreciated!