Persistent Pain Previously Occurring From Time To Time Ie Every

Persistent pain previously occurring from time to time ie every few months lasting 2/4 days now pretty much all the time relieved by strong ish pain killers and rest with warm bottle on area which is just below left shoulder blade recent investigations of chest X-ray and upper abdominal ultra scan show nothing.
Other history 15/20 years ago. breast cancer partial removal and radio therapy, left kidney removed, removal of gall bladder and a hysterectomy . Only conclusion of now problem is muscle strain but not helped by physio. Any suggestions?