Unusal Spotting...

Hi for the past 2 and half days I have been have been spotting on and off. Sometimes there is justa spot of blood but others times there is more...I am cd21 and am 4dpo. I have both endo and pcos; and this was my forth and last round of clomid 150mg. I dont usually get spotting between af that last this long Im also geting af type cramping and endo pain (which only usually bothers me majorly 3 or 4 days b4 af)...could af be coming early? I know I only ovulated 4days ago coz I use opks....