Ovulation Dates

I used to use the app Flo and according to that my ovulation day was Sunday just gone.

I swapped to this app today put all my previous periods and data in and according to this app tomorrow is my ovulation day.

However according to Glow my ovulation day has already been too?

I’m a little confused as to what’s going on...

I’m now getting aches and pains and things like that so I’m not sure if I’ve already ovulated or not as my discharge is becoming thicker and less sticky.

Can someone just maybe explain why 3 apps have given me different dates.

Thank you x