I have a new fever after being sick with the flu-should I be worried?

I was sick with the flu for about 4 days--fever 102-104, deep cough, stuffy nose, body aches, headache, and severe fatigue. My fever went away for about a day and a half and I started feeling better. Today my head started pounding again, I have a low-grade fever and I'm still congested with a bad cough.Is this normal after having the flu, or am I getting sick with something new?