What should I do about a cough that won't go away?

A couple weeks ago, I caught the flu epidemic that has been going around. The worst is over, but I still have a very bad cough. It hasn't gotten better, it has become for severe and frequent. Cough drops and cough medication don't seem to work. This has always happened to me. When I get a cough, it takes at least a month to go away. What should I do?