Rather than answer you all through the comments, I'd thought I'd write another post. But first, thank you so much for your warm wishes and congratulations. I really appreciate them, especially since I'm still in shock.
Yes, this will be #3.
And no, we weren't trying. You could even say that we were actively NOT trying. But apparently we are very, very fertile.
We had left open the possibility of having a third someday down the road, when we were more financially stable. I guess "down the road" is relative, because it feels like we've only gone about a block. And honestly, we really didn't think we'd get to a point where we felt comfortable having another child. I guess it's a good thing we've got 35 weeks (or so) to get used to it.
Of course we will love NewBaby and of course s/he will have clothes and such. But once again I'll be scouring Craigslist and garage sales for baby stuff (having sold and given most of ours away already) instead of my imagined shopping sprees at BuyBuyBaby. And that's okay. I know NewBaby won't care.
To be honest, I'm pretty much swinging between excitement, fear (I won't have enough hands! We don't have enough money!) and nausea. I guess that's normal, right?