It could be that the best treatment is simply practice. As difficult as it is, there is power in "putting yourself out there" and leaning in to the discomfort of speaking in situations where you aren't comfortable. The goal is ultimately to build your sense of self confidence, to the point where you don't even have to think about your speech before talking. The only lasting, sustainable way I've ever known to do this is by getting the experience (even if it means falling flat on the first several tries). It's not the easiest way to learn, but when you get over the hump, it's the most real and sustainable solution, as opposed to any other gimmick out there.