What is this??

After "trying" (not preventing, but also not tracking ovulation or timing anything right) for 2 years I finally got pregnant. I ended up miscarrying at 6w5d. My husband and I were both very sad about it obviously and it convinced us to actually start tracking and trying to conceive again. I have had one fill period after the MC, and am now almost 2 weeks late with no positive pregnancy tests. However, I have been spotting old blood (no pink or red) for 6 days. Nothing to actually fill a pad.. minor cramping but nothing serious. has anyone else experienced this? should I call a doctor? Or should I just consider this a period and count cycle days from here?