I just heard from the nurse: It's all good!
I have un-clenched.
The nurse said the doctor doesn't know why I would be having such an early period, but assured me that the blood test showed that I'm "nicely repressed" and everything looks fine to proceed as planned.
Additionally, she gave me the dates and instructions for when to start my injections. My first one will be on Thursday, November 15th (in just over a week!). I was so delighted by this news I quite literally kissed the phone as if it was the wonderful messanger nurse.
I don't know why I got so upset. Actually, I do. It's because I am so used to my body not cooperating, especially reproductively. It never does what it's supposed to do - this strange birth-control induced period is a great example of that. But for all the trouble I've had (I'm talking to you - yeah, YOU, ovaries!) I can't complain anymore. Knock on wood, things are progressing...swimmingly.
Thanks again, all, for your support and for talking me off the proverbial ledge yesterday. Love you guys!