back pain is most commonly related to muscular spasm or weak bones.I suggest you see an Orthopedic surgeon who will provide a likely diagnosis after doing a clinical examination and some relevant tests.It is also advisable to take frequent breaks from the sitting posture even if the pain is not manifesting at that time.Apart from a diet inclusive of seasonal fruits and vegetables,some exercises like Suryanamaskar and swimming are especially useful for backaches.But please consult an Orthopedician before starting these.