When I was miscarrying I was spotting off and on. It was only when I wiped and that was just sometimes. At sometime through the off and on spotting when I wiped I passed the baby. I had no idea. I didn't have cramps or anything. The sac was still left and I didn't want to wait to see when I would pass that so I opted for a d&e. Some women are different through there pregnancy though. My cousin had bled every month for about a week up until she was 12 weeks pregnant. She said it was kinda like a period everymonth just a bit lighter. So there is hope for women who bleed in there pregnancy.
It can depend some women begin to spot first it could be like a week or two befor the m/c even happes. Once it does typically you bleed for 5- 7 days but every woman and pg is different. Some situations you can bleed forever or not for long. A miscarriage is painful severe cramping and heavy bleeding the days you do and usually have alot of clotting. I hope this helps and good luck to you. If you think you are having a m/c I would go get checked out by your dr.
AP