I experienced flu-like symptoms from 5 pm to 9 pm everyday for years. It was due to depression. Depression can actually cause those kinds of symptoms. I didn't know that at the time. It was exhausting! I, too, had to cancel evening plans or just not make any.

As Winter4me said, if these symptoms coincided with starting your med(s) or changing the dosage, do call your doctor right away. If not, then it could be depression.