You'll have your answer soon- I'm sure you just need a few more days to figure out what's happening for certain. You could be experiencing pregnancy spotting, which is not uncommon around the time of expected AF.
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Just as a side note in case you do not get a confirmed BFP, spotting prior to AF (while not pregnant) is not considered normal and is often a sign of low progesterone. How many months have your had your cycle back since your LO's birth? It's not uncommon to have short LP's, spotting, etc. as your body regulates after birth and while breastfeeding. But that can mean that TTC can be more of a challenge. Have you considered charting to see what your cycles are fertile?