What Is The Cause And Treatment For Perisitent Cough

I have had a cough for a month. Started like a cold or bronchitis. Went to family dr. Got a shot of antibiotics and steroid. And givin a z pack. That I finished. A week later not feeling better but worse went back to Dr. Got another shot of both, another week of antibiotics and steroid that I took for a week lowering dose. Went to Africa on a safari taking my meds with me. I went back to .dr. When I got home and got a chest ex ray to test for pnomonia and got another round of a stronger antibiotic and 2 more shots. My cough is tighter and deeper.