What you describe doesn't really sound like it is heart-related, but of course you want to be certain. One thing that argues against it being your heart is the constant discomfort; another is the fact that the back pain can be reproduced by breathing (never a heart problem). What it does sound like, in fact, is possible asthma, which can present insidiously, causing a sense of tightness or pressure in the chest as well as causing sorness in the auxiliary muscles (which often are affected in the back as well as the base of the neck). The sensation going down your arms is unclear as to origin, and I generally subscribe to the conservative approach, meaning rule out the serious stuff first. For that reason you might want to have an EKG done, just to be sure there's no atypical heart symptom showing itself here, but I feel, based on the description of the thoracic symptoms that you could have new asthma (or perhaps bronchitis, even). Then again, it could all be muscular.
Once you've ruled out the biggest concerns, the lesser ones don't seem quite so worrisome.
I hope this is helpful. Best of luck to you.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist