What Causes Stuffy Nose,cough And Fever?

I had a fever of around 100-103. I had my nose burn and have alot of pressure so much that my eyes are watering. I have a bad cough and a stuffy nose. I went and had a check for the Flu but it was negative and I had my flue/swineflu shot. After around 4 days my temperature suddenly droped to around 96-98 and im sweating. Whats wrong with me? and what can i do to help?