Miscarriage

So we went to the dr for our first ultrasound Thursday nov 2 (9w 5d) unfortunately they couldn't find the heartbeat and the baby is only measuring 6w. This is my 3rd miscarriage so kinda know what to expect but it sure isn't any easier to accept. Anyways, my question is has anyone gone through a natural miscarriage and how long did it take? My first i had a D&C; at 12 weeks and my 2nd I was only about 5 weeks and it passed super fast. My dr wants to do another ultrasound next Friday just to double check and make sure there is still no heart beat. She said I am 3 weeks in and could possibly start cramping/spotting anyway now. It's been 3 days since finding out and still nothing is happening. If any of you have experienced this how long did it take for you to start showing signs of miscarrying. I just hate the waiting game it's killing me.