I would also recommend a trip to the doc, as the flu should not last that long. The after effects (fatigue, etc.) of the flu may last that long, but major symptoms such as fever, lymph swelling, etc., should not.
For initial outbreak of the flu, nothing works better than Oscillococcinum, a homeopathic remedy. But you need to take it within the first 24 hrs. of the flu's onset for it to be effective.