It is not uncommon to experience some spotting and mild cramping during pregnancy, especially in the early stages. In your case, since your doctor has already assessed your symptoms and deemed them as potentially being caused by old blood from implantation, it may not be a cause for immediate concern. However, given your history of miscarriage, it is always best to err on the side of caution and consult with your doctor for further evaluation and reassurance. They may recommend additional tests or an ultrasound to ensure everything is progressing well with your pregnancy. Remember that every pregnancy is unique, so it's important to communicate any concerns you have with your healthcare provider for personalized guidance and support throughout this journey.