I have Done Something To My Back and It Is Bad. That said, it's just acting up in the way it has acted up periodically since I broke it over twenty years ago. This is miserable, but it follows a predictable course, and will likely run its course over the next week or two and leave me none the worse for wear. In the meantime, living at a seven on the infamous pain scale saps the joy out of life, alas.
I think I got glutenated, also (and perhaps related?). My weight is up five pounds, and it would explain the foreboding out of nowhere. Stupid gluten.
This too shall pass.