What Causes Heavy Vaginal Bleeding After Having A Miscarriage?

Hello. I had a miscarriage at 6 weeks. A scan showed an empty womb and nothing left over that would require a D&C. I have been bleeding heavily (the same kind of flow as after my two previous births). I have been using tampons, but now read online that this is not recommended. Can you tell me if this is really a serious issue. I'm working every day and it would be more than inconvenient having to use maternity pads right now.