Azithromycin - on my 3rd day of using and I'm still coughing, how long before I get better?

I have been on azithromycin for 5 days and still have the cough and spoke to a friend of mine that's a nurse and she told me that the cough can stay for at least 3 weeks.

You should be noticing signs of improvement by now if the cause of your cough is bacterial. If the cough is caused by a virus then the azithromycin will be of no benefit. There is very little you can do to help a viral cough. A good cough suppressant may help - talk with your pharmacist. Be sure to drink plenty of water and rest so that your body can fight off the virus. If you are concerned about your lack or recovery please see your doctor again.