So - u say this presentation was just announced and was not listed on the syllabus as a requirement, yes? If so... go to him ASAP! explain your situation, say that if u were aware of the obligation of public speaking aa part of the course u would have approached him earlier in the semester to explore some kind of accomidation - acknowledge that you don't want to be treated differently and that you don't want to shrug your obligations to your group - but that the short timeline between hearing of this obligation in conjunction with obligations to other courses has you fearing your final grade may suffer as a result of this speach issue you have been struggling with for X years. Am 90% sure they will "have a heart" Pls let me know how it goes! Good luck with finals! :) U got this!