Diaphramgmatic breathing is a very good option to improve fluency. Stuttering is basically caused by the brains inability to properly process the speaker's voice as s/he speaks. When we use another voice, we stutter less. That is why we stutter less when we whisper, sing, speak in unison or speak in a falsetto. That is also why speech prosthetics are so powerful and help so many people. That is also why certain programs which use diaphragmatic breathing or other voice chhanging techniques work so well. This is also why standard stuttering therapy which frowns on these techniques is often useless. The more you use diaphragmatic breathing the easier it will become and your fluency will improve. Keep up the good work