I had been on speech therapy, when i was like 7-8 y.o. We practiced speaking by syllables (making a pause after each one). I dont feel like it helped me. I didnt want to speak by syllables with other people because its awkward. I feel like its more of a breathing problem. Like, other people can naturally control their breathing without thinking about it, but i cannot. Thats how i imagine it. Long sentences are much harder to pronounce for me. While reading oftentimes i have to breathe in on every word to read them. But in reality, breathing may not matter and it really is only about state of mind. I remember, when i took amphetamine, i could speak fluently and i didnt have to control my breathing in any way.