Brown discharge/blood?

So i recently started going on the birth control pill, im currently on my placebos and i’m on my period... but i noticed that my period looks like old blood and i’ve been on it for 4 days and it hasn’t changed.(my period only last 5-6 days) At first i thought it might be implantation but i have blood clots and it looks/seems that i’m just on my period. Im not sure if this is normal or a side effect of BC ? Am i just overthinking? what could this be?