What Causes Brownish Bleeding With Severe Cramps?

i started birth control, loestrin fe 24 about three weeks ago, i took it the first day i got my period, and then after about four days my period stopped, and ever since i randomly have brown discharge, its not heavy, just uncommon for me, and i've been having pretty sever abdominal pain, its not cramps really, its more of a constant stabbing pain? is it from my birth control or is something else wrong?