Based on your answers, some of the most likely causes of your back pain include
fibromyalgia
ankylosing spondylitis (or related conditions, called spondyloarthropathies)
a viral infection (as may occur with the muscle and joint pain during a flu).
Other, rarer, causes are also possible.
While over-the-counter pain medicines, a heating pad, and rest balanced with activity may be helpful, it is important that you see a physician> to evaluate these symptoms.