I am so sorry for your loss! I have had a miscarriage before and I understand how hard it is. There are so many different reasons for a miscarriage and the best way to help determine what caused it is blood test. The reason for the wait is to give you body time to recover and hopefully give you a better chance of having a healthy baby in the near furture. Good luck!
I'm sorry for your loss
If you have an infection while pregnant it can cause you to lose a baby, but so can many other things. There is no telling why you lost the baby. The dr may be able to do some blood work to try and determine what may have happened or you could have had an incompetent cervix.
If you lost a lot of blood this could be one reason why your doctor wants you to wait a little bit, I've also been told that if you become pregnant to soon after losing a baby it can increase your risk of another miscarriage.