If you are experiencing bleeding later on, after 10 days have already passed, you can assume that it is the early onset of menstruation, or a very early miscarriage. Very early miscarriages, that take place even before your period was due, are very common. In fact, they may make up 50 percent of all pregnancies. Another important observation surrounding implantation bleedings which happen when the fertilized egg has started to implant itself into the lining of your uterus, which is rich in blood and tissue is that we are talking about extremely small amounts of blood here. The amount of spotting that you notice during an ovulation bleeding should be much smaller than what you see when your period has just started.
Now, onto the question about the duration of an implantation bleeding. Some women literally only see a spot of blood, meaning that the bleeding factually has no duration at all. Only a third of all newly pregnant women will experience implantation bleeding. In my case, it happened only during one of my pregnancies. Indeed, the bleeding was so minimal that I would not say it lasted for any time at all, and I have heard that this is true for the majority of women. Medical literature will tell you that implantation bleedings can last up to two days, though, and that the amount of blood varies slightly. If your blood flow ins increasing, and your bleeding lasts for longer than two days, you could be having miscarriage symptoms or another medical problem, and the best approach would be to contact your doctor to make sure everything is OK.