Oh my God, my story is exactly the same! I'm even the same age. I started stuttering when I was 3 or 4, but it was mild and didn't affect my life much, to be honest. But when I turned 14, my stuttering changed. When I was 14, I started masturbating, and that's when the disaster happened. I couldn't even say my name, which also starts with a difficult letter, and I couldn't say some letters. Now I'm 17, and I masturbate every day, and my stuttering hasn't gotten any better. I felt strongly that the problem was from masturbation because the change happened at the same time I started masturbating. Now I'm sure of it, and I'm going to stop masturbating. If you want, we can DM and encourage each other to quit because my story is literally the same as yours.