Hmm. I have spotting before AF, maybe 1-2 days before she arrives, and it's very light. Typically I only notice it after BDing or if I check my CP (which I typically stop doing after Oing). I have a 13 day LP, never gotten my hormone levels checked, and never been pregnant. I had a shorter LP up to about 6 months after stopping BC pills, but now I seem to have gotten more normal with time (I haven't taken anything other than daily vitamins since). I feel like I'm normal with my pre-AF spotting, but who knows?
I'd definitely suggest getting a doc to check things out if you're concerned, though. If anything, do it simply for peace of mind. But it seems like your LP is fine.