Based on your answers, some of the most likely causes of your back pain include
degenerative joint disease (also called osteoarthritis)
polymyalgia rheumatica (PMR)
a viral infection (as in the aches and pains of having the flu)
a muscle strain
a compression fracture related to osteoporosis.
Even with this long list, there are other possibilities as well.
While over-the-counter pain medicines, rest and heat may be helpful, it is important that you see a physician to evaluate these symptoms.