How do I really know if I have mis carried?

Hcg /ultrasound. Drs. Usually repeat the levels of blood chorionic gonadotropine. If the levels drop it is likely miscarriage. Other possibili is to have a ultrasound o see if there is an embryo in the uterus.
See doctor. Vaginal bleeding while you are pregnant is a sign you might be having or had a miscarriage. If you think you had a miscarriage, you should see your doctor. They will be able to do an ultrasound to check the contents of your uterus. You should also know what type of blood you have as you might need an injection called Rhogam to prevent future problems. I am sorry for your loss.