Ovulation change

Kayla

Okay so I had EWCM on CD 13. Had sex. Positive opk CD 14 am and pm. Had sex. App showed ovulation as today. This morning took another opk and it was negative but then my ovulation day changed to yesterday. It did this last month too. I’m planning to have sex again tonight (it’s our 9 year wedding anniversary!) I just don’t get why it would change to yesterday if my peak was yesterday, it should be today right?