HI, i was prescribed zpack for 5 days to treat a sinus infection that has a lot of drip that causes cough. After I finshed last Friday, but Monday I developed flu like symptoms, diareahha, chills, severe exhaustion, yet I have not missed a day of work. Loss of appetite, depression and anxiety. I have never had an allergic reaction and the coughing has caused a pain in my left side breast. COuld it be that I cought the flu because I was run down or is this from the medicine. I am a very healthy 54 year old female - very fit and look much younger. I feel like I have mono I am that exhausted. Coughing subsided but feels like chest is full. Could I have caught something else because I was run down?