Brown blood

My period is over it ended the 22 I started my birth control the 23 back again I take it every night and still I go to wipe when I pee and it's like brown stuff not blood it's mucasy kind of what is that? And there's a small chance im pregnat because it was not a "period" it was more spotting I take a test april 18th to find out im 15 what could it be?