What Causes Brownish Discharge During Menstruation?

my period usually last for 3 days and now i am on my fifth day. my period is light and weird looking. it looks red some what but when i put a tampon in it has a bit of weird brown on it.
i am on the pill and i have been for almost a year.
i am also on my fourth regular hormone day.
is this normal? what should i do?