I'm an SLP who stutters. First, I'm genuinely happy for OP that they have a strategy that seems to work for them. Sometimes, individuals might have a breath support issue that is separate from stuttering and fixing that issue may help with speaking because breath support is improved. This is rare in practice though. There is a good article that addresses breathing and stuttering, and how there is no evidence showing a significant link between changing your breathing (such as switching to diaphragmatic breathing) and increased fluency. (https://stutteringtherapyresources.com/blogs/blog/its-almost-never-breathing) From my perspective, what has worked for me and my clients, and what the research literature tells us, is helping a stutterer learn to understand, tolerate, and ultimately accept that moment of stuttering creates the most benefit and increased fluency. That in itself will decrease tension, avoidance behaviors, and fear of speaking. If you really do suspect your breathing is impacting your speaking, probably best to see a physician before changing the way you breathe.