Anyone want to speculate?

So I’ve been testing with opks since cd 10ish. I have gotten MANY so-close-but-not-yet-positives. I am now on cd 21 (typical cycle 32-36 days with the occasional 40 day + cycle) and I’m having verrrrrry light spotting tonight. So would you put your money on ovulation spotting (which has happened to me like twice), implantation bleeding (which has never happened in 3 pregnancies), or suuuuuuper early af (which has never happened to me)??

Here’s my opks for reference! Also I hurt THE SHIT out of my back today and have taken lots of Advil and icy hot. 🤷🏼‍♀️