Came back to my desk and read your comments, which almost made me cry again. The spotting had stopped, but based on your wise advice I decided to call my doctor anyway, just to be on the safe side.
Things moved very quickly after that.
When my doctor called me back, she asked a few questions about the spotting. Then she asked about my job. I told her I could work from home if I had to. "Okay," she said, "I want you to pack up everything and go home right now, and don't come back to the office until you have had no spotting for two weeks."
Two weeks?!? Her logic: I am not having a miscarriage (she said this with the utmost confidence), but every time I move around a lot I get red bleeding and I freak out. If I can work from home, it is better to do so and save myself the panic. I couldn't argue with that.
So I had to tell my boss, of course--actually my boss and my several supervisors, who as it happens I was supposed to be meeting with right at that moment. I was incoherent and teary and not at all the smooth, polished professional I had hoped to be when breaking this news, but they were totally understanding (if a bit stunned) and sympathetic. Then I grabbed a bunch of files and caught a cab home.
And here I am.