What Causes Discharge Of Blood And Brown Stuff Persistently?

I am on birth control bills and I had my period 3 weeks ago like a normal period, going on 4 weeks. well i first started my period and i discharged brown at the beginning, as usual and then at the end of my 6 day period, as usual i discharged brown again. well i get up go to the bathroom and when i wipe i keep discharging bllod and brown stuff. this has been going on for about 4 weeks now. what could be going on?