Spotting / bleeding?

Wasn't sure where to post this but.... I ovulated on oct 17. And had small spotting that Ive never had. Oct 24 (today) I noticed some small spotting like a few drops. Mild cramps that went away. And for the past few days I've been feeling nausea on and off. My period is due nov  1. I had unprotected sex oct 22. Was wondering if anybody knew why I was spotting like this?? 
Btw, my periods are extremely heavy and my periods are painful. Normally if my period comes, I get horrible cramps and when my
Period starts... it starts and doesn't come light so i don't believe that's what this is.