Hi, I am Dr. Ravi Nayak, Orthopaedic Surgeon from Mumbai. As I understand you have acute backache which has also occurred in the past. At your age, this can most likely be due to pulling a muscle in the back. It can happen due to lifting heavy weights, improper posture or sitting for long periods of time. It could also result from a slipped disc or very rarely, structural changes in your bone called spondylolysis. I suggest you consult an Orthopaedic surgeon, who will examine you and possibly order some tests like Xrays of the back, and later, an MRI, depending on your progress.