Why Do I Still Have Chest Discomfort, Fast Heartbeat, And Minimal Cough, Could It Be Something Other Than Bronchitis?

I went to urgent care to receive treat/ diagnoses on chest discomfort, fast heartbeat, a slight minor cough that I have to force out and nausea when I would bend over. I have a slight pain in my left arm and sharp pain every now and then in my back. My heart tends to beat faster when I lay down. While at urgent care a received an EKG, chest x-ray and had my blood pressure checked. The doctor said everything was clear and fine. I received a steroid shot and a shot for nausea and also a nebulizer treatment. The doctor when on to say that it was bronchitis but I haven't coughed up any mucus at all. I really don't think it's bronchitis what should I do?