Just think of your past before 4 - 5th standard .... Speaking was easy, fun but what happened after that ...have self Introspection and you will know that it's your anxiety, fear and pressure to perfect is the reason. The thing which you are trying to 'stop' or ' hide' your stammering is the main reason it still there. Speaking doesn't required any force, it's a natural flow , but here we are getting stuck in block, Try to manage your stammering , it will go by itself , manage means if you have block try tricks such as skipping 1st letter in word or saying it in different way but there is a catch , you should not think it as a way to hide or defeat your stammering think it as a shortcut or a way to ease your stammering. Blocks are hard but there several techniques like bouncing(saying first world until you get whole word), prolongation. You can feel the difference when you speak alone and outside. It's the urge of Speaking and our thought of saying the words which makes thing worse. Instead focus on meaning and purpose rather then Speaking . My personal trick is that I focus on lips and flow of air through it and always keep my hand on stomach to avoid tightening and speak in pauses. I don't think of people now as I used to , I have De-senstitize my self a bit and it helped me a lot.