How Long Does a Miscarraige Last? Why Cant they give me any definate answers???

This has been one of the most difficult , painful, and confusing two weeks of my life. After successfully carrying and giving birth to 3 children, I have been experiencing a miscarraige, which to my shock is not a one day or even one week situation.

At six weeks i noticed light spotting, mostly brown. The doc did an exam and determined 'implantation bleeding'. Though this was somewhat of a relief, the cramping continued as did the spotting for 6 days. Then after that, light bleeding, which turned to what seemed like a moderate period.

A trip to the ER gave the diagnosis of 'possible miscarraige' and blood hormone levels suggested it

Two days later, back at my OB, an exam, blood test, and ultrasound sent mixed signals. On the one hand, at 7 weeks they are not able to see much so there was no visable heartbeat or baby and on the other, my blood had a significant amount of pregnancy hormone that wasnt dropping appropriately.....

I have a scan scheduled for tomorrow in the early am and today am in what may be the worst pain i have ever felt (aside from active labor)

is it completely irrational to hope that by some miracle the baby could still be viable? how much blood is too much because i dont even fill a pad in an hour and total bleeding days is 14. :(