Hi there ~
I understand your concerns. Smoking
marijuana may cause you to have a variety of different and unexplained symptoms. Your shoulder and arm getting sore may be related to marijuana or another medical condition. You can find out if it is a medical condition by quitting the use of marijuana. I also believe that you may need to take a break from the crazy schedule and have yourself be seen by a psychiatrist, relating a thorough history and getting a physical examination, testing with lab work as well as maybe imaging studies to help diagnose the condition. The first step however is to consult a psychiatrist
I hope this helps. Take care and have a lovely day!