Thanks for all the rational words of support. Sadly, I just don't have a good feeling about this.
On the side of this is doomed:
Another negative this morning.
Feeling pretty crampy. Not cute little twinges, but real cramps.
On the side of there's still hope:
Still not spotting.
Breast tenderness has had a resurgence.
On the whole, and based on personal prior history, I'm leaning more towards doomed.