Weird cycle... anyone experience this before?

Hello.

On Tuesday I started spotting, used a pantyliner and by Wednesday I was needing a pad. Changed for hygiene reasons but altogether I probably could’ve gone w one pad for the day considering the flow. Yesterday (Thursday) my pad was clean all day. Today (Friday) I had heavy spotting earlier in the day and by 5pm nothing.

Any ideas what the deal is?

Also- would i mark Tuesday or Wednesday as the beginning of my period... and when is the “last day”... so confused!