Help please! Dpo vs period

Karen
I see so many women say that they take an ovulation test at 11 or 12 days past ovulation however I am at 11 days past ovulation and yet I still have eight days until my missed period. So I took one tonight (CB digital) and it was negative. 
My question is do I go by days past ovulation or days leading up to my missed.? I am very confused and any help would be really appreciated!
Ovulation June 27
Expected period July 18th
11dpo