@thutmosechen You certainly may have a condition of tight muscles as your doctors have suggested. It's very common for us to develop patterns of tightness in our bodies from our posture, activities, and any injuries that affect us. I happen to have tightness through one side of my body and it does affect the expansion of my rib cage and one side doesn't move as much.

What helps this is to have a specially trained physical therapist release the tightness. This lets the body move again as it should, releases dehydrated tissue that is stuck, allows fluids to circulate again, and it can relieve pain that is caused by the tightness. My PT has released my respiratory diaphragm before which helps me breathe. I have tightness in my shoulders that can pull the first rib upward, and it gets stuck, so that changes how I breathe. and I have tight fascia between the lower rib cage and my pelvis that she works on. I have thoracic outlet syndrome, and it does affect breathing.

Here are a few links, about TOS, and our discussion about myofascial release therapy.

- Neuropathy - "Myofascial Release Therapy (MFR) for treating compression and pain"
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/
Thoracic outlet syndrome
https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/symptoms-causes/syc-20353988
J Manipulative Physiol Therapy

. 2020 Jul-Aug;43(6):606-611.
doi: 10.1016/j.jmpt.2019.10.006. Epub 2020 Aug 21.

"Respiratory Dysfunction in Individuals With Thoracic Outlet Syndrome "
https://pubmed.ncbi.nlm.nih.gov/32829949/
Does this sound like something you want to explore? It is hard to find a specialist who understands TOS, but you can find doctors who treat this condition at larger medical centers such as Mayo that list Thoracic Outlet Syndrome as a condition on their website that they treat. Therapy for TOS is usually long term.