Implantation bleeding or AF?

Nicole
Okay so, 11/9 to 11/13 was my last period and this months period is supposed to be from 12/9 to 12/13, but for the past week or so I have been experiencing light spotting (from light pink to dark blood tinge). Then the day before and the day of 12/9, the spotting completley stopped. But yesterday and today I have had dark blood tinged spotting but it only shows when I wipe. I also feel a really tiny form of cramping. I am not on BC and I have no idea if this is just an abnormal period or implantation bleeding. When should I take a hpt? Since I'm ready past my expected period date?