So on Day 10 of my cycle I started testing with Clear Blue Easy (the one where it's either just "surge" or "no surge." Saturday morning I tested with that and came up negative. That day I bought the other Clear Blue Easy OPK - the one that will give you low, high, or peak fertility. I tested the same night with that test and came up with peak fertility. The next morning I tested with the first OPK again and it came up no surge.