My shoulder hurts a lot and it's worse when I breathe, what can I do?

Hello, my shoulder has been very sore for the last 3 days. It's worse when I breathe. Two days ago, I went to the emergency room because the pain was unbearable. The nurse gave me tylenol and advils. My pain subsided. I was still going to stay and find out what was wrong. But they told me there was an 18 hour wait, so I left. But now the pain is still there. I tried to make an appointment with my doctor but it's going to July 21! I also tried to find an appointment at a walk-in clinic on Hello Health but they have no appointments available.