Okay so I really need help ladies

Lisa

on October 26 I got my period and on October 31st it ended I took a ovulation test on October 31st that's the first one the second one I took today and all the rest so I'm trying to understand why it went from being positive today and now a few hours later it's no longer positive and on the app it says I'm fertile starting November 7th (test from left to right)