My 4 year old sons cough for 2 weeks?

My 4 year old son has been coughing for about 2 weeks. He has been diagnosed with asthma about 2 years ago and is on Albuterol and Flovent inhalers. They have seemed to work, but over the last 2 weeks his coughing has been more consistent. The inhalers are not working and we are questioning if he really has asthma. His cough is more like a dry cough with flem instead of a shortness of breath associated with asthma. We are very frustrated and don't know what to do.