@anony - I've never had the discipline to use OPKs religiously - so no, using them doesn't work for me.
The spotting has continued overnight, if not a little heavier. I feel like this is the start of AF. At day 21? This just seems so unfair. I am also not prepared for it either.
I'll be having my 21 day BT on day 23. But now if this is AF, I don't even know what to make of it.