Hey, I had a problem with these 2 years ago when I had a project to present at work, but this problem appeared since I was in the school, but at school I was with my classmates and teachers that I know and they could understand me. I have tried a lot of things and I am ready to share with my experience: I started to speak a lot and train myself in front of the mirror, read books and record your voice and listen it to understand where you have problems and should work to improve yourself.