Congrats on #51. On the shoes, I've been on the treadmill most weeknights since the time change. I have shoes that I don't really like outside, but they feel great on the treadmill. Guess since there is more cushion on it?

Aside from the shoes, your back may be sore just from all the boxes etc. that you've had to move in the past couple of months. It should make you stronger, but it also put a lot of stress on muscles that don't normally get worked in the same way.  You also haven't been doing as much (any?) Pilates to work your core since before you moved.

No Pilates whatsoever and it shows.  We have the studio but we haven't had the time yet.