I Have Been Having Excess Secretions From My Throat. Coughing

I have been having excess secretions from my throat. Coughing up junk off and on for over 2 months. Went to the er last Saturday with complaints of not being able to breath, two days before visit I had a pain like from my heart all the way down my left arm. The next evening it was like someone had taken a hatchet and stuck me between the shoulder blades. They ran the blood test to see if I had a heart attack and all the lab work came back normal. They did a cat scan and they said the lungs and heart looked ok, but that I had gallstones and should follow up with my primary care doctor for them. Gave me two shots and sent me home with two prescriptions. Started feeling better by the second day. But these were 5 day does of antibotics and steroids. By yesterday when the doeses decreased greatly the cough, mucus, and everything else is back. My left lung hurts none stop and it's an area as large as a grapefruit or larger. What could possible be causing this. BTW I am under tremendous stress.
The lung or chest pain does not come and go. It's constant