Do you tend to sit for a long time? Like in front of a pc for hours?

Shoulder pain related to breathing can originate from the spinal and rib-cage joints in different parts of the neck and thorax. If you feel the pain at the tip of the shoulder, then its likely to be called back shoulder pain.

There are facet joints in the corner angle of the neck and shoulder,when strained, the pain will be felt over the back of the shoulder,chest and upper back.

Long hours sitting down with the head hanging forward will cause the joints to be strained. This is because the neck needs to support the weight of the head.

That being said, you will need to fix your sitting position or stand up every few hours.