Good you are getting it checked out as it seems to be repeat pain ... do you have a cough with it at all?
Sometimes I have problems from repetitive movements. Or if sometimes if you are doing exercises incorrectly, say push ups for example, you can pull or twist a muscle. Or even sleeping in a different position or on my pillows differently causes issues.
I have to say rolling my back against tennis balls does help relieve some of my shoulder & back pain.
Hope they find solutions for you soon!