So According to my flo app I'm four days late I have taken tests last week negative then at least and I don't get it

How long are your cycles usually? Could be you just ovulated a bit later than usual. The apps only estimate ovulation etc if you aren't ovulation testing, and if you have longer/irregular cycles they are even less likely to be accurate.

So you use ovulation tests? These apps aren’t that accurate without them

I haven't tested ovulation ever

I used the app to get pregnant twice but now my cycle is weird due to my loss in February and surgery