I have a question, when you speech block, do you feel the urge in your chest like a tightness in your chest making you not be able to say the word? If so, try to exhale through your nose and say that word, that way you’re forcing air out of your body that won’t come out while you’re trying to say the word. The sensation of that feeling in your chest is air not escaping and just waiting there, it needs to be released to say the word. Your brain has gotten subconsciously used to not allowing air to flow through certain words that begin with those letters. So if you keep on remembering to do that, it’ll be embedded in your brain. That’s what I do for me and it works.