There are many possible causes of low fever and bone pain all over the body all the time, and the common ones are as follows: 1. There may be rheumatic or rheumatoid arthritis. This kind of disease, once the attack, may be accompanied by pain in the bones, joints and muscles of the whole body in many places, and there are symptoms of fever. 2, may be caused by septic infection of the bone. For example, if a patient has chronic septic osteomyelitis, he or she may have a low-grade fever and bony pain in many parts of the body. 3. If a patient has tuberculosis, he or she will often show a series of symptoms such as low fever, hot flashes, night sweats, and wasting. If there is a tuberculosis lesion in the bone, there may also be bone pain. 4. It may also be caused by tumor-related lesions. For example, when a patient has a metastatic tumor, he or she may experience similar symptoms. Finally, this condition may also be caused by a series of unexplained infections or autoimmune reactions.