Spotting after period

I finish my period on Wednesday (today is Friday) and I’ve noticed light pink traces in my clear discharge, this happened on my last period aswell. My periods have also started coming a day earlier even though I’m on the levest pill and have been for almost a year so my periods always come at the same time.

Does anyone know why this could be or has it happened to them before

I am also sexually active if that helps aswell

And sometimes I forget to take my pill so I double up on the next day