From what I can see in the xrays you have a pulp stone in 45 and distal proximal caries 45. The caries could be the reason of sensitivity. *Considering that the xray is of the RC treated 46. Although these two are obvious and your dentist must have checked those but just pointing them out again. Your ear needs attention first. An infection there could tend to cause other problems. First complete ear treatment. Meanwhile you can use an anti sensitivity tooth paste twice daily and fluoritop mouthwash at night before sleep for symptomatic relief. Also if you have a habit or reading or spending long hours on phone your back neck muscles could strain and cause back of neck, back of head, jaw, ear pain etc. You can confirm this if you have pain in back base of skull area radiating upwards and downwards.

Your dentists might be right and wrong too. It could be Idiopathic dental pain. Cause of the pain cannot be detected.

Hi .. to find out the reason ,thorough  clinical examination and history  recording is to be done..  POSSIBLE REASONS MIGHT BE.. - regarding the sensitivity in your tooth 46 may be due to excessive  testing with bite pressure, (checking whether there is pain is there or not) which may cause  teeth supporting periodontal ligament hurt ( apical periodontitis) .any tooth which is root canal treated will have mild sensitivity on tapping ,pressing and  chewing.. please don't test the tooth repeatedly the pain will subside slowly..if pain is more take a dolo  650 tablet once or twice -Regarding the pain in neck may be due to myyofacial pain disfunction syndrome in which the pain is vague which is more during early morning wakeup  u will feel all ur muscles of mastication and neck muscles  aching. The reasons  for MPDS may be stress or clenching of teeth or due to TMJ and teeth anatomy  disharmony.. which be decreased  by using soft splint of 2 -4mm thickness during  day and night time and following yoga and meditation.. avoid hard foods and one side chewing.. do regular  mouth exercises  like mouth opening and massage the muscles of mastication. All the things what I have told might not be exact diagnosis may vary on clinical examination and history recording..