Wow, I am actually going through the EXACT same thing as we speak. Yesterday was slightly cramping and bleeding (dark brown). I went to the ER and was examined and my levels were fine and my cervix was also closed. He figured it was my cervix preparing itself or the placenta.
Today I've been bleeding heavier and more red, but my cervix is still closed. They are just scheduling an U/S for me. My doctor acted as if it was definately a M/C. But I've heard of so many people that have killer cramps and bleeding and things turn out fine, that it's hard to give up hope.
I'm curious to what your levels are tomorrow, as I'm surprised they didn't find anything baby related when they did a scan. Not even a sac?
i would follow up with your doctor because it does sound like a MC but i could be wrong. the doctor will be able to let you know more info.