What could it be?

Period is not for another 2 weeks my last period was apirl 25th and ended apirl 29 and then i only had sex once this month which was may 2 . so my app is telling me tommorw is ovulation day and i took a ovulation test and it came out neg i usaully have the discharge before ovulation but today i start bleeding or spotting at first it started out to be light pink and then it came out to be a dark brown just few mintues ago ive never had this before i never even had it when i was pregnant with my first. So does anyone know what it could be ??