@gabbys24 In my experience, thoracic outlet syndrome can cause chest pain that can be confused with a heart issue. It's a stress related problem with tight neck and chest muscles. It's like living in a straight jacket. I have had ribs twist because of spams which are painful in the chest and sternum. I have had a neck spasm start and go into my chest which is quite painful, but after massaging it, in a few minutes, it subsides. Since you have already ruled out a heart problem, it could be a physical problem like TOS. For me that also causes one side of my chest to not expand fully. What helps for physical therapy is myofsacial release. Here are some links that you might find of interest. It is hard to find doctors who really understand TOS. Look for them at teaching medical centers like Mayo or Universities with medical schools that treat TOS.
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/
https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/symptoms-causes/syc-20353988
https://trainingandrehabilitation.com/how-truly-treat-thoracic-outlet-syndrome/