Before you do this, however, there are a couple of things you should do.
Firstly, you should talk to your regular doctor or medical practitioner, the person who is presently charged with keeping your pain under control. Understand that when you do so, they may not approve of what you are thinking of doing, especially as by seeking the help of a hypnotist, you are to a certain extent rebuffing their assistance.
Trust me, it is possible that your doctor will react in this way - if they have been treating even sometime, you probably know them better than most, so you may have an idea of how they are likely to react already, but it could happen.
But the fact is, you are not there to ask for their approval or recommendation. What you need to know is whether subjecting yourself to hypnotism poses any real physical health risks, whether for example a pre-existing medical condition could be exacerbated by the experience.
In effect, what you are looking for is the medical all-clear so if your doctor does not approve of the idea of you seeking hypnotism for any reasons other than those which are strictly medical, it is your decision whether you choose to listen to them.
Secondly (and assuming that you decide to go ahead with trying hypnotism), you need to find a hypnotist who is capable of treating the problem that you are going to present to them. Whilst most professional hypnotists or hypnotherapists are going to be able to deal with more 'run of the mill' demands such as people who want to stop smoking andso on, not every hypnotist is going to be capable of or comfortable with the idea of dealing with chronic pain.
Consequently, you may need to contact a few appropriately qualified professionals to see whether they can help you. Pay them a visit to see whether you can get along with them, whether they are convincing when they suggest that they can help you and so on.
In short, you need to feel 100% comfortable with the hypnotist or hypnotherapist you are planning to work with because if you are not, there is an immediate element of strain or stress introduced into the relationship which is not going to help you to achieve the results that you're looking for.
The second alternative is to learn self-hypnosis. And if that sounds crazy, prepare to think again!