you have the exact type of stutter that I have, words the begin with e o a k t after a few blocks, I feel exhausted and my vocal cords are tired if that makes sense I don't have any solution for you as I am struggling with the same curse my whole life, but try soft onset where you say these letters in a softer way. it definitely makes saying these letters/words easier but I can't imagine being able to use this technique in public, in my opinion it is not possible to use this technique unless you are extremely relaxed and speaking quitley, which is simply not applicable in most real life scenarios