Low grade fever, upper muscle back pain, fatigue?

Flu: Could just be the flu. Try some over the counter meds for pain and fever, and if not better in a few days see your doctor.

Evaluate it: Although a serious condition is unlikely, it should be excluded. Most likely this is related to persistent inflammation triggered by some sort of environmental exposure (previous or on-going). Toxins can be infectious (viruses, bacteria, yeasts, fungi, mold and parasites), chemicals, toxic heavy metals, even toxic electromagnetic radiation. Environmental medicine deals with this.