@happyat76– I know that pain! It sounds as if you have Costochondriitis. An injury could have caused this too. Long ago I stepped off a pier to hop on our boat at low tide and slipped. My husband grabbed my arms and I slammed against the gunnel. You bet I hurt it!! It took several months to heal. Yours could be caused by something else entirely, even an infection. Have you had recent blood work? If not I urge you too.
This site might help a bit. https://www.mayoclinic.org/diseases-conditions/costochondritis/symptoms-causes/syc-20371175
I hope that your breathing machine will make you happy again!