You may have a muscular imbalance that could be tested by physical therapy.

The most common cause of back pain in young people is muscle weakness or overexertion. I suspect yours is muscle weakness. Google Williams back extension exercises and do them 2 or 3 times a day. Take advil 600 mg 2-3 times a day. Avoid prolonged sitting. If you are no better in 4-6 weeks, then see an orthopedic surgeon.

Hope it helps!!

Dr. Bose