possibly tmi but advice please

My period was due Saturday which is about day 41 of my cycle. I have pcos so I'm never exact but always around this. I have had spotting a few times a day since Saturday. I normally have spotting the day before my period starts but it hasn't started. The spotting was red to start but is now more browny colour. I took a very cheap pregnancy test yesterday afternoon which was negative. Any ideas what it might be?