Apps to track fertility ????? Help!

Kari
Hey everyone. Does anyone have more than one app they use to track fertility days?  At this time I use 2. This one and ovia.   I'm just curious because they are off By about 5 days!  So I feel like I have to use my opk for like 12 days (which can get exspensive.. And annoying!) 😫. Anyone else have this problem or any suggestions ?!