Dude that’s so awesome that you’re trying. Keep at it. You didn’t say you were looking for suggestions but practice in a mirror. Don’t look away when you get those blocks. When you find yourself coming up to a block, literally just pause and say the word to yourself in your head until you feel comfortable. Then calmly say it out loud. Even if you still block it’s completely okay. Lastly, I’d also let your professor know that you have a speech impediment. That way if there are any blocks in the recording they will not be marked against you.