It's cold to sleep under the tent. I have a damp-proof mat, a small shop and a sleeping bag, but I still feel cold back pain. Please ask the Great God to solve it.

I want to say, if your waist already hurts, it's useless to add any blankets and quilts. Cold and damp poison have invaded your waist. I suggest you see a doctor as soon as possible. If it is inconvenient, you can ask someone else to rub your waist for 1-2 minutes, so that it will be hot. But this is a palliative, not a long-term solution.