Hi Pixel - and welcome to our forum.

I used Sharon Butlers stretches at my worst {03/05} and still do at times as needed.

I also go to a very good chiropractor and a PT guy was great help when my top ribs & collarbones were stuck and getting pulled up into my throat. {felt that way anyhow}.

Now my main sx I think are some latent TrPs in my upper back muscles and the pec minor adheisons. And of course if I raise my arms forward or up for any length of time or lift certain ways ect.

The adv PT guy gave me a more advanced version of Sharons laying out on the floor stretch.
His idea was to lay on a firm rolled up towel or a 6-8" foam cylinder.
You lay on the roll - along the length of the spine- use a small pillow if needed for neck comfort
knees bent to ease low back pressure

place arms at a comfortable postition and just relax into the gentle stretch

this will open up the chest area, drop the shoulders back and down
with out any active uses from yourself

At my worst times I did this 2-3 x a day for 15 min or more
and still it is my basic thing I do when I feel that I need it.