How long does it take?

This is my first pregnancy, about a week ago is started spotting brown discharge. Yesterday the ultrasound confirmed an empty sac measuring 6 weeks (I am at 8+4 based on my last period). We have been told it is most likely a blighted ovum but to come back in a week to be sure. While it is devastating news, given my health history We are unfortunately not surprised. Yesterday into today I have been getting stronger cramps and slightly more discharge. Has anyone had any experience on how long it takes to go from cramping and spotting to bleeding with a miscarriage from a blighted ovum at 8 weeks? Any advice or words of preparation are welcome?