I had a Large ovarian cyst around a year ago where I started birth control to try to shrink it. However I am now experiencing pain and brown discharge?

Big or little pain? if BIG pain, go to the ER and get it checked out. Birth control does not shrink the cyst sometimes and just prevents new ones from happening... if little pain, then maybe just a cyst popping. brown discharge from that cyst popping. No worries unless BIG pain or fever.