Suggest Treatment For Chest Congestion And Cough With Excessive Phlegm In The Throat

Hello! I am on week three of having chest congestion that seems to be caused by lots of sinus drainage. I do not have itchy or watery eyes, my nasal passages are pretty clear. My phlegm is white to light yellow. I am a professional dancer/teacher and when I do physical exercise I am short of breath and cough a lot. It s really affecting my ability to do my job. And I can t sleep well at night with all the coughing. A walk-in clinic doctor gave me prednesone steroid and said after a couple days if I didn t see any improvement to take an oral antibiotic. I did both and am feeling worse. I am also taking mucinex which seems to help during the day some. Should I be just taking an antihistimine instead? I really am not feeling well. Thank you.