What Causes Persistent Cough With Headache?

Two weeks ago, I had what I'd say was the flu. Achy, exhausted, sinus crud. Nothing really wrong with my stomach. Wasn't very hungry but that's about it. Low grade fever. Slept most of the weekend away. Since then, it went into a cough that has begun to subside but the exhaustion will not go away nor will the headache. Still have plenty of mucus as well. Is this something that I should go to the doctor over or should I just let it run it's course?