I had a subchorionic hematoma in early pregnancy and bled bright red almost everyday for 5 weeks more than a period. I was told by my doctor that he has never seen on not resolve itself. The bleeding is caused by the sac separating a little from the uterine lining I had heard of people who bleed so much that it causes it to completely detach but other than that it doesn't really cause a miscarriage just annoying bleeding. If I was you I would contact my doctor and get testing done to see what could be causing the miscarriages.
I am currently suffering from a subchorionic hematoma and have been quizzing my Doctor about why this happens. I've been told over and over again (by ER Drs, other Doctors, and my OBGYN) that this is completely random and no one knows why this happens. It's really hard to accept when it happens to you. I've been told there was nothing I could have done to avoid what happened, and nothing I can do to prevent the loss of the baby (if that happens). I showed symptoms at week 11 and am now at week 13. I hope that your Doctor has something more insightful to tell you, but the one thing I know is that what happend is not your fault and you probably did everything right.