I suspect the main culprit is the too-soft couch I've been sleeping on since I moved into my current place about 2 and a half years ago. I was letting Bunny sleep on the bed. After last weekend's attack, though, I've commandeered the bed and she can sleep on the couch. (Actually she sleeps on a different couch, which is firmer and more comfortable.)
Anyway, I'm getting a custom-cut futon cushion delivered, which - if I've measured correctly - should fit over the seat area of the overstuffed couch and make it usable at least for sitting on. Meanwhile I've been taking care of my back by avoiding the soft couch, plus massage and chiropractic. This coming week I should be fully back in action.