Polygraphs are typically used in corrective settings where one is going through the legal system for therapy. You may be referred to sex offender treatment, even if you have never sexually abused a child or viewed sexual abuse images. If you have nothing to hide, you have nothing to fear from polygraphs, because they are typically more an interrogation tactic than they are a measure of how truthful you are being: Their accuracy depends on the examiner and their experience.
Plethysmographs are a specific test to give your therapist an understanding of where your attractions lie. These tests may be disturbing to you, but should not be cause for anxiety. They can help you understand what populations you are most attracted to. One test should be sufficient, but may not be covered by insurance in some places.
Arousal reconditioning describes a variety of behavioral methods to change what you are sexually attracted to. You can read more about this method here
. These methods are controversial both in terms of effectiveness and ethics, and can be a hotly disputed topic even among therapists. Many therapists do not agree with using this method, as it can cause severe psychological damage and some even consider it to be a form of sexual abuse. It is better to avoid therapists who use this method.