Child Having High Temperature, Severe Dry Cough, Tiredness, Low Apetite. What Could This Be?

Hi. I took my 9 year old to the doctor last Tues. because she was complaining of a head ache, upset stomach , and sore throat . The doctor said it was probably a cold and to treat her with over the counter meds. Since Tuesday, she has had periods of okay feeling but she has been very tired, her appetite is off, and she has been coughing like crazy. So much so, that it has about drove her father and I crazy. This afternon she started complaining about feeling bad and then developed a temperature of 103. I took her to the minute clinic and the nurse said that she was worried about a secondary infection because of her high temp and that she found it perplexing that she started her systems with a low grade fever and now almost a week later she has the high temp. She said her lungs sounded fine and reccommended we take her back to her doctor in the morning. The constant coughing is worrying me. What could be causing her continuous dry cough along with her other systems?