Serious question

Marge

I have 2 apps to track my cycle one says im ov today the 28.the glo app said i ov on the 26th. Got a pos opk on the 26 but it wasn't very strong,neg opk today the 28th sex on the 25th. What do u thnk happened. Glo unusually never right with any of my days. Could i could have conceived and thats why my test today is neg?