Why do none of the app line up together?!

Question

I have multiple period/ovulation tracker apps but none of them are in sync.

Glow says ovulation is today.

PreMom(the opk kit Im using) says tomorrow.

period calendar says the 16th?

￼this is my opk chart. 
So confusing idk when I ovulated or if I have?

Answer

If you want to be sure when your ovulation occurs you need to be doing OPK tests. Don’t stress yourself out with a bunch of apps as they are only estimating based on averages and not you as an individual x

Answer

Taking your bbt and ovulation tests should help them line up after positive ovulation test or after temping all month

Answer

This is my opk chart

Answer

Because it’s literally just a guess.

Why do none of the app line up together?!

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