Backache could be due to pinched lumbo-sacral soinal nerves. This can happen due to overuse of the lower back
as in work requiring too much of bending, lifting weight, fall on the back, overweight, canal stenosis, bone disease, spondylosis, poor posture etc. Poor posture while sleeping, sitting on computers or jobs for a long time, uneven bed, exposure of back to cold air while sleeping can cause a discomfort for a few days. Please consult a neurologist.