My husband and I are TTC, I have extremely regular periods and never any spotting at all. So, we had sex 4 days before, the day of my period, and the day I got off - which was Sunday. Monday afternoon I had some pinkish spotting, and now tonight (Tuesday) I have dark brown spotting. I'm also really tired, my back is killing me, and I have a headache with a little nausea. Is it possible I'm pregnant and still had a period this month?