Brown period blood ??.

So the beginning of this month I got on birth control “the pill” and I’m supposed to start my period in a week from today but I started today and like 4 days ago I noticed that I was spotting brown blood. And today since I started my period it’s more and very heavy. And I know it’s my period because I’ve been cramping a lot and red blood is mixed in with the brown blood. I’m just wondering if I’m the only one who

Has experienced this????