When will miscarriage start after no heartbeat?

Melissa
I am between 7-8 weeks and was told yesterday there's no heartbeat, and although there's blood flow to my uterus there's none to baby. I go back in two weeks if I don't miscarry naturally. Just wondering how long it usually takes after no heartbeat. And a few questions, when it's about to happen will i just feel cramps or what? How long will the bleeding last? Will I be able to see the baby or will it be too small? I was too upset to ask my doctor anything at the time. Thanks