I can tell you from experience that you have been involved in heavy lifting , perhaps in the nursing profession or some kind of manual work.  If you continue to work it the pain may also go down the other arm and is excruiciating pain because a nerve is trapped in your cervical vertabrae.   You must finish work and rest, your G.P. will or should send you for a cervical scan, no more carrying shopping or lifting anything, only rest and eventually ,

the pain will ease, and become managable without operation, which is the last resort,