This is probably well known but it seems like spotting is often treated as a good sign on here. In fact:
"the chance that spotting will happen on any given DPO is greater for non-pregnant women than for pregnant. In DPOs 0-9 this means that spotting is a slightly negative indicator for pregnancy.
In DPOs 10-20, in contrast, it is a strongly negative indicator since the primary cause of spotting in those DPOs is oncoming menstruation. The large bulge in the non-pregnant curve shows this clearly."
See graph here - www.countdowntopregnancy.com/early-pregnancy-symptoms/spotting-during-luteal-phase.php