I don't know. I used to have extreme anxiety about paps and stuff, and something clicked when I was like 15 and I went from freaked out to okay about it. I think I got scared about diseases or something and that made me forget to be afraid of the exam. Then when the exam was not particularly horrifying I wasn't scared of any that came after.
You might could distance yourself from your personal experience by using the opportunity to guide your doctor (or let her guide you) through the details. Most doctors narrate what they're doing anyhow, but if not you can prompt them, and communicating what makes you uncomfortable can help you feel more in control even if you can't change any of it.