CONFUSED?!!

Can anyone please offer some help & info if possible please??

Basically my last 2 cycles have been every 24 days... yet it’s only today by working it out I’ve realised this & put a pattern to my cycles as of late... according to this app AF isn’t due till the 22nd yet last night & today I’ve had light pink & brown spotting in & off... I first thought this could be possible implantation bleeding as app says my OV day was on the 8th of this month yet I am starting to think my OV date was in fact the 5th (my bf & I did the deed from the 5-8)

What’s my chances of this still been a possible implantation bleed or is AF arriving??