I can't really help much. I spotted at around 6 weeks with my last one, and then it went away. My m/c was at 14w...so I really don't think the spotting was a warning sign.
I would call your doctor and talk it over. Maybe they can run some tests to make sure everything is still okay. The only thing I can think of is to make sure you are getting enough fluids.
I hope this one sticks for you