Spotting?! Discouraged, what could it be?!

So I got my first ppaf back in June. My cycle lengths have been all over the place since - 34, 37 and 29 days. I usually spot a day or 2 before periods but this cycle I’m on day cd 30 and I’ve been having very faint pink discharge (or spotting) when I wipe going to bathroom since Monday 10/23. Also some sporadic cramping.

I was so sure it was ib so I took a pt yesterday and got a bfn. Still no af today but still faint spotting. I mean, it’s so faint I have to look closely most times. What could it be? Could it still be ib this long? Could it be something else?