I have a 30/31 day cycle that usually starts off with some brown discharge and then it goes full scale red flow. Lasts about 5-6 days.

This cycle I am so confused

12 DPO - woke up to brownish pink discharge on my underwear. Disappointed I put in the cup and waited. Turned to slightly red when wiped later that evening. Cup wasn't getting full even a day later

13 DPO - brown and red streaks in CM but not much flow. Like day 1 of a period. Didn't manage to fill a cup in 24 hours

14 DPO - absolutely no discharge in the cup. Red blood on my fingers while cleaning myself

15 DPO (today - 1 day late) - woke up to an empty cup. Again red blood only when I wipe. Still waiting for the red AF flow to begin. Not much yet.

Assume the flow will begin today but not sure yet.

Which day is considered Day 1 of my cycle? Hoping to understand how long my cycles are. Coz after months of tracking i still seem to get it wrong.