The Evoked Potential test sounds like it would be a good indicator of an organic injury. I suggest you push through it and deal with the symptoms. You do want evidence of an organic injury. You can't fake it so the results need to be considered seriously.

I don't believe you when you say it could set you back months. It may wipe you out for a week or two. I've been through that. You are not improving so what are you afraid of.

"Hey doc. I want to prove to you that my symptoms are real but I will not do any tests that cause my symptoms to manifest."
Explain how that fits with any research methods.