So sorry.
I had my first miscarriage in July (have 3 kids already) and I went for 7 week scan and the sac measured 4 or 5 weeks and was empty.
That was on a Monday, I intended to go back the following Monday but woke up on the Sunday with pinkish colour on loo roll. Carried on with my day as didn't know how long things would take. Light period by lunchtime and built up a bit.
By the following day it felt almost like a normal period although lighter. I was taking DD1 to her swimming lesson and I felt really lightheaded and had some cramps, and then went to the loo and passed some blood (seemd like a couple of gushes) with some quite bad cramps (only period pain like) and then carried on with my day.
The bleeding seemed to get a bit lighter day by day after that and no more pain.
A couple of weeks later I had a negative pregnancy test.
I only realised with hindsight but I think the swimming pool blood was it, the moment when the sac passed.
So for me things took 6 days to happen from the scan, but only about 36-48 hours from pink blood on loo roll to passing the sac. Had a week of light bleeding after that. None of it was even as heavy as a period apart from the blood gushes when the sac passed.
I don't know if I got away lightly? Hopefully yours will be quick and painless too. I had read loads of scare stories and was expecting a lot worse.
One thing I did do as soon as I realised from scan that the pregnancy was not viable was to carry pads and spare clothes, water, painkillers and a pack of wipes, just in case. Thankfully not needed but allowed me to carry on with life confident I could cope with a crisis.
I am sorry again for your loss, I hope things happen naturally and painlessly for you. My sac was under 1cm too, maybe at that size the physical process can be less harsh.