Stuttering

Hello everyone. I have stuttering. In my life I do not stutter with my friend and family. I stutter only if I need to present something. In couple of days I will have a defense where I will need to present in 45 min my work. I know that I will severely stutter. I got prescribed with Xanax. I took 0.25 mg pill one hour before the presentation where tried to present to my friend. I was stuttering. It did not help me at all. I have never taken Xanax. Do you think before the presentation I should take 1 mg to make sure that I will be fully relaxed? Or what size should I take?