I used to be really scared too, to the extent that I would wriggle so far down in the chair that the dentist couldn't reach my teeth. I was terrified of every single thing that happened, like drills and tightening those clamp things for molar fillings, not to mention the injections.
I decided my fears were pretty unnecessary but were due to not understanding what was being done, so I got a job as a Dental Surgery Assistant ie the 'nurse' who hands bits and pieces to the dentist and cleans everything up in the surgery. It meant that for the 18 months I worked there (for my own dentist) I learned a huge amount about what's going on in the mouth and during treatment. It also meant that I couldn't possibly be such a wimp in front of my employer, especially as she did my teeth for free in our lunch break.
For me, my way around the fear was to face it head on. Understanding each step of the process has meant my fear has gone and I have even had small fillings done without an injection
I hope your dentist can get on top of the problem for you John and cure the pain - dental pain is awful as it's right in your head and you can't get away from it.