I've had lower back pain for a while -- it's generally been focused around the sacrum and I know how to deal with it. This is new and different and I don't like it. And... umm... the only person who's going to be massaging me there is DH (and if it is SPD, I'm guessing he's not going to be getting much action of that sort either ).
I've been searching back on MN and it does sound very much as though what I have is early stages of SPD. A couple of posters described it as feeling as though you've come off the seat of a man's bike and landed on the crossbar with your groin, and that's exactly how it feels.
Most of the posters seem to think that the NHS belts are a bit rubbish, too (you have to wear them under your underwear, but also take them off to sit down, apparently... so that will fit well into a normal lifestyle, then).
Also a non-user of baby shampoo here -- water is fine and new babies smell lovely, at that end at least...