I read through the ParaGard pamphlet and nothing suggests that the release of the copper will cause your Vulvodynia to come back. Any amount of copper released by your IUD should be normally excreted through your bile-- provided that your body does everything right.
You can ask your doctor more questions and you can also read through this pamphlet for more information on each and every single side/adverse effect that may be caused by the iud. http://www.paragard.com/images/ParaGard_info.pdf
Best of luck,