Early period

My period wasn’t due until April 13th . But I started brown spotting April 7th for the first 2 days and then Saturday it was more of a period but dark not bright red. And I’m still having the spotting. And it’s back to brown unless I wipe it’s super mucasy with red. Which I’m assuming that’s my period. But why was it that early? Right when I went to test to… when I updated my “period” it changed the calendar. According to my body and not testing I believe I would’ve actually ovulated the 31st