I suggest here instead of treating the pain treat the cause. I know phantom pain or stump pain is difficult to cure but its not impossible. If you do regular exercise for your emputed limb with increase blood circulation to nerves and soft tissues it should start reducing. Similarly for neck as well back pain check the issue why its there?. Is it a spinal level problem?, or is it a muscle and bone weakness? Either of this case you need to visit ortho and physio and get it evaluated properly and based on the evaluation take proper treatment program. Only treating the pain, it may not be helpful. To answer your question, for about pain killer drug, here I Dont know about your complete health report and condition, as well past history like since when you are having problem? So can not give medication here. But can give you general guideline that is use hot and cold pack frequently to have some more pain relief with soothing and anti inflammatory effect on soft tissues. Take care