What Causes Difficulty In Breathing Along With High Anxiety Levels?

I am having trouble breathing and have high anxiety because of this. The doctors did x-rays, ekg and blood work but can t find why. I am currently taking Flonase and Amox/K. They feel I may have an infection. I am also taking Benadryl to help me sleep. In the last 5 weeks I have not been able to sleep more than 2 to 4 hours a night and have to sleep practically sitting straight up. The doctor prescribed Xanax for the anxiety but I am afraid to take it. Can it interfer with my breathing even more?