You could have had what is called a Threatened Miscarriage. There would be some degree of bleeding with cramping or lower backache. This bleeding is often the result of implantation. There is nothing a doctor can do especially since you were so early. I personally wouldn’t think it was a miscarriage. It all could just be your period. You can and do pass clots when you are on your period.Remember, Stress has a big impact on your hormones. This can cause you to be a few days late. So can a lot of other things.
If the bleeding gets heavy, like soak through a pad an hour, then I would make a trip to the ER. There is no treatment for a miscarriage this early so seeing a doctor is pointless.