Confused by OPK

Ceci

My cycle is very regular and glow predicted that I would be at peak fertility today. I took my opk today and got nothing. Last month it was spot on, high fertility on every day that glow predicted (CD12, 13, and 14) and peak on the day that was predicted as well(CD15). We baby danced a lot during my fertile window, but I still got my period on the day af was due.. Now on CD14 and no sign of fertility.. I'm so upset and confused.