For years and years scientists and researchers have studied why people stutter, and unfortunately there is no exact cause that can be identified. Stuttering is considered to be a speech impediment. One method to consider would be to slow your speech and take more time before you speak. This has been proven to help tremendously, but takes a lot of concentration. Here is an interesting fact, it is said that one who stutters is said to be smarter than others.
One thing you can try and do is to think ahead before speaking. This will allow your thoughts to fall in line with your speech. What this will do is help you speech automatically fall in line with your thoughts. To stop stuttering today, you can begin by thinking before speaking rather than pausing after speaking. If you slow down and pause before each word, then the speed of your speech will normalize.
Try thinking over and rehearsing in your mind what you plan to say and how you plan to say. It would create a blueprint in your subconscious mind. When you would begin to speak, the sentences will follow in a pattern and it would roll out from your subconscious mind. You can do some aural visualization that would increase your optimism and confidence for the speech. Aural visualization will help you to literally mentally visualize each and every word you plan to say in your speech.
You can stop stuttering if you can gain back confidence. And confidence comes fast and quick if your thoughts are patterned. If your speech is patterned with your thoughts, the flow will be spontaneous and you would stop stuttering. Mentally, you should weigh, listen to and rehearse the sounds of each word you say or plan to say.