CW, I too am so sorry to hear about your loss. I suffered two losses myself, so I know how difficult it can be to deal with. The bleeding you described a few weeks ago also sounds like AF to me. I'm a little confused about why your dr is prescribing provera as well since it seems like AF is not quite late yet. I would be concerned about the continued spotting, especially if an u/s confirmed there is some type of blood inside. You said your dr ran several tests that all came back normal. Do you know if they ran another blood pregnancy test to confirm your levels were all the way back down? If not, I would definitely request that.
I wish I had some better suggestions to offer you. All I can really say is that I'm as stumped as you are.

Maybe somebody else will be able to respond w/ better input than me. I will say though, that if you aren't comfortable w/ the way things are being handled, don't be afraid to ask your dr questions. Make sure you understand why everything is being done & that you agree w/ it all. If you still don't feel comfortable after asking questions, there's nothing wrong w/ getting a second opinion.
Wishing you all the best!! Please keep us posted.
Holly