I also used to face these and it had ruined my school days. I am 21 now. Let me tell you that I used to read aloud articles and practice my speech quite sometimes. I didn't see results. But then, I went for a holiday where there were no one I knew. I felt a surge in my confidence and I spoke in simple and clear sentences. I think it's all about perspective and your state of mind built over the years. Travel a lot and always speak simple sentences. Forget the fact that you stammer and change your state of mind. Sooner or later you will see the difference.