heavy dark brown bleeding not on period

I’m 22 years old, been on birth control since i was 15, also have PCOS but this is the first time i’m experiencing this really heavy and thick dark brown bleeding while i’m not on my period. it’s not spotting because it hasn’t stopped for a couple days and i’m freaking myself out looking up the things it could be  on google so does anyone have any idea?? i know brown blood is considered old blood but i haven’t been sexually active recently so i’m unsure why it would just start out of nowhere. i also have abdominal pain and cramping. anything helps. thanks.