Ovulation question

Hey ladies I know this glow app is set up on an algorithm but this is my first cycle inputting positive opks.

The last few cycles AF came right on the expected day( 28 days cycle). But now that I input pos ovulation it’s pushed period date back. Now I know ovulation determines AF but if I assume I ovulated the last few cycles then the date should be the same and not change

On a normal 28 day cycle I am supposed to start tomorrow but it says I don’t start until Sunday. But if AF doesn’t show tmrw, am I still technically late?

I see feel prego can’t explain it. Had tugging and heavy uterus for the past 3 days. Today it stopped and now tingling boobs and increase CM.

Any thing that could help me would be great!