I too have had hypnotherapy for other reasons (stress and anxiety) and found it wonderful, so relaxing. The guy was a pyschotherapist too and he was so helpful. I have also wondered if this technique would help with my pain. I see my pain clinic dr next week and may ask him about this.
As other people have said you need to make sure the person you see is properly qualified. You also need to be receptive to hypnotherapy. As with everything some people just don’t respond.