This is a discussion to have with your doctor
. It sounds like you have had a very difficult time with back and shoulder pain! From your complicated history there are many different possibilities for what is causing your back pain now. First, pain with taking a deep breath can be associated with inflammation of the lining around the lungs (called pleuritis). This can be caused by an infection such as bronchitis or pneumonia. It doesn't sound like you have any other symptoms of infection (cough, fever, trouble breathing etc), but it will be helpful for you to be examined by a physician. However, what sounds more likely is that you have either a musculoskeletal or neuropathic (or both) component to the pain. If you have a pinched or irritated nerve in your back or upper arm that could cause pain similar to what you describe. You may also have alignment problems in your spine from the car accident which have led to early arthritis
in the spine or shoulder. You may also have pain coming from a primary shoulder problem, such as a tendinitis or a muscle sprain/strain or even a tear. In order to determine which of these many possibilities (or maybe even more than one!) is involved, it will be important for you to start with your primary care physician
for thorough history and exam. This will help suggest further tests or specialist referrals may be needed.