after intercourse is not that uncommon, but I suggest that you schedule an appointment with your OB/GYN. In general, blood after intercourse can come from three different locations. The first location, is from within the uterus. This is blood that you would see during her menstrual period, but can occasionally start or show itself first after intercourse. The second, and most likely source of this blood, is from your cervix. The cervix contains blood vessels that are somewhat fragile and can break easily during intercourse. This is especially true when you are pregnant, and perhaps the recent miscarriage has caused your cervix to become somewhat more friable. Finally, the last location the blood can come from is your vaginal wall, but you should know this because it would be painful.
Again, I would suggest that you schedule an appointment with your OB/GYN. He or she can perform a detailed physical exam including a pelvic exam which is an important part of determining why you are bleeding. In addition to determining why you are bleeding, the two of you can discuss your recent pregnancy and whether or not it was desired. If it wasn't, then you the two of you can discuss what method of birth control
is best for you. If desired, then the two of you can discuss the best methods for you to achieve pregnancy again.