Ovulation date keeps changing...

Megan

This is my fourth month using fertility friend to track my bbt. I got a peak opk on cd 14 but my temp didn't rise for several days after. I'm frustrated because ff keeps changing my ovulation date. Yesterday it said that I o'ed on cd 14, then today when I put in my Temps it changed to cd 16.

Has this happened to anyone else before?

I'm hoping for my bfp, but so far this chart looks pretty similar to every other one that I've had.