Hey man, for what it's worth, you have a beautiful voice that deserves to be heard. Now, for your blocks, I've been there. Others have already provided you with great links to tools and experts. I can only share my "trick" : exercice. Like strenuous exercice. At a moment of the day, close, but not too close to your event. You need to exercice your body to release all of the stress hormones and load up on endorphines. To me it helped. I felt strong, I was breathing deeply naturally. my mind was calmer because I "forced" it to harmonize with my body. I still had blocks here and there, but I didn't car, and not caring relaxed me. In any case, you got this!