Well, looking at your past charts, I see that this is the first time you may have ovulated in a long time. How far postpartum are you? Are you breastfeeding? If all of these things are coming into play then it is no surprise that you're having irregular cycles with difficult to interpret CF patterns, spotting, and more erratic temps. While it's not common to bleed with O, it is one of those things that can just randomly happen one cycle and never again. So it is possible that you O'd on CD 20. Your temps support this better than CD 15. While your CF doesn't line up well with CD 20, that could be attributed to breastfeeding and postpartum regulation. However, if you did O on CD 15 then the spotting is likely caused by hormonal fluctuations- the same hormones that caused your temp to dip below the coverline (a surge in estrogen, dip in progesterone).
So, unfortunately it's a waiting game. I see that you've taken several HPT's. A lot of women have to wait until 12-14 DPO to get accurate results, so if AF doesn't show within the next couple of days then I'd test again. If you still get a BFN, then I'd assume that you O'd on CD 20 and start your counting over again. Good luck and keep us posted!
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