Shoulder and back pain left side for over a week. Heart rate near 100 most of yesterday. Palpitations no shortness of breath or arrhythmia. Worried?

Get checked. No way to tell if this is anything serious, you need to see your doctor to determine if this is a heart problem or pulled/strained muscle. Good luck!
Best to be seen. I suggest having a visit to evaluate your symptoms of shoulder and back pain. It is possible that the pain is muscular, and is causing anxiety with a rapid heart rate. However, if you have heart inflammation such as pericarditis, lung inflammation, or hyperthyroidism, you could have these same symptoms. The only way to evaluate is to be seen.