Generally a virus runs a higher temp and may for a short time leave you feeling down but as long as you are moving air and coughing up the offending mucus you will start feeling better. 

The fever not going over 102, back pain, and greenish - gray productive cough - all sounds like a possible bacterial pneumonia or bronchitis.. This can be  accompanied by shortness of breath (possibly even elevated blood pressure). You won't start feeling better til the infection starts being controlled. Get thee to a medical doctor...