Ovulation spotting? Help!

Casey
My period came early on 8/20-8/25. I have been taking opk since 8/27 all of them have been negative. On CD10 i BD and used Preeseed. Yesterday on CD11 I started to have some light pink spotting, I only see it when I wipe. It stopped last night and then today it started again CD12 which today is the start of my fertile window..... what might this be?