It's called stutter blocks and I have the same case. Yeah, it's so tiring, in my case blocks are physically painful when I try to get my words out. Holding my breath or taking a deep breath does not help. But I found a temporary solution for me, maybe you should try it out, it's better with a face mask but I get used to without it. Before I speak my words out loud, I chant them in my mouth silently. I repeated the words in my mouth, it helped me ease the pressure and help me out my words. You don't have to open your mouth a lot just do it a little so it won't be obvious. They won't notice you