Trust me when I say this: it gets better. You just have to change your mindset and speak very softly and comfortably as if you were presenting in your own room. Do focus on presenting slowly and accentuating certain important words. I've struggled a lot with the same issue, and most of it stemmed from not respecting myself and my voice enough. I needed to learn to slow down (quite ironically, this is the advice people who are complete laics in the topic of stuttering give us). Even if a presentation goes awry, you need to know that next time it will work out. There is always a turning point. There are always highs and lows. I wish you good luck!