What illness could this be?

So I caught something around friday night, and when I woke up Saturday morning, I had a fever and a sore throat. No big deal, it's just a cold I thought. Pretty soon I developed a cough, and my throat was getting worse. My coughs were full of phlegm and then i developed a stuffed nose. I slept 18 hours a day and it was pretty bad. Now it's Tuesday, and I still have a fever and a stuffed nose and the cough is still there. My throat is a little better. Should I begin to worry? Should I go ask my doctor what to do?