do you ever lay out on the floor and just let your shoulders relax down and the chest & pecs will gently stretch and loosen?
with arms out at a comfortable place - maybe a very mild stretch.
I use a yoga mat for a bit of cushioning {laminate floors}
That helps my neck loosen up too.

a new thing chiro is doing -
places my arm behind and across my back, then massages deep in the soft front of the shoulder area and around and under the scapula.
the first time he said - "you might think I am killing you" LOL
but it wasn't too bad just pretty tender, and since then just feels good

I should look it up to see where/what he is working on there- haven't got around to it.