Kelsy's cough

Kelsy has been out of school for 4 weeks. It started out as having the stomach flu the two days before Thanksgiving vacation. Then on Thanksgiving Day she came down with a cold. Poor thing had her eyes and nose running like crazy. She had a cold for about two days, but the cough has lasted forever. It is so bad she can't go to school because it is a constant cough. I'm talking about a cough that is dry and she coughs every 30 seconds to 2 minutes. She is so sore from all the coughing. We've been to two different doctors. Done chest x-rays, tried asthma inhalers and nebulizer treatments, phenegrine with codeine, honey/lemon tea, honey/aloe vera juice tea, cough drops, everything. Nothing has stopped it. The only time she has any relief from it is when she is sleeping. The doctor has finally given her a strong antibiotic, and it is helping a little, but she is still coughing prolificly.