What Causes Sporadic Sweating And Chills Along With Fatigue?

Last week I had a stomach bug (low grade fever, vomiting, diarrhea) that was over in about six hours (I believe it was a stomach bug and not food poisoning because my son came down with the same symptoms three days later). Yesterday morning I woke up with another low grade fever (100.3) after a night of sweating and chills. I was fatigued but had no other symptoms and the fever eventually lifted. Today I had an outpatient nasal procedure performed (sphenocath with lidocainie injection of the sphenopalatine ganglia nerve) as a treatment for my chronic migraines. The ENT put me on a Z-pack and so far I ve taken one dose. Tonight the fever is back. I ve also felt bloated and have gained about five pounds in the past week, for no apparent cause. I am 39 years old and in reasonably good health (low cholesterol and blood pressure) except for chronic migraines. Should I be concerned about this recent fever, weight gain, and fatigue?