OPK REMINDER LADIES

I see the question being asked all the time, I didn't get my positive OPK did I even ovulate? We don't know. No one knows. 
***Ovulation prediction kits do not test for ovulation. Ovulation predictor kits measure the LH surge that precedes ovulation, but can't confirm whether you have actually ovulated.***
so if you don't get a positive OPK all that means is you didn't catch the surge that happens before ovulation, not that you didn't ovulate at all. only a ultrasound or temping can predict ovulation. start testing as soon as your period ends because yes it is possible to O as soon as day cd8. 
 it is more likely that you missed your surge by going off the "average" fertile window. good luck ladies!