Feeling sick one day, starting to feel better the next, and then suddenly feeling awful again can be frustrating. If you are experiencing flu-like symptoms that come and go, you may wonder whether you have the flu or if something else is going on. Symptoms such as fatigue, body aches, chills, headache, congestion, and fever can fluctuate throughout an illness. Sometimes this is simply part of your body's normal response to an infection. In ...