I read or heard or saw somewhere that some women need to test a few times a day or they may miss their surge. I don't know about where you live, but where I live the OPK"s cost over $50 for a 5 pack... and I can't afford that kind of addiction!!! I bought 2 packs and no luck for me... got lots of faint lines and a couple withno lines at all. Bizarre.
You may just have missed the surge, but your chart looks good so far...
When in doubt just BD like crazy