Speech blocks were a massive problem with me for years, what helped me a lot was telling people (my friends and strangers) that I stutter. This helped me because after doing so, I no longer felt as if I had to be fluent. I now felt as if my listener would give me time to talk because they knew that I was a stutterer. Aside from the above, I also work very hard to speak slowly and deliberately. Sometimes with speech blocks because I know which words I block on, I tend to avoid them however, through speaking deliberately I've found that I can say these words. My experiences were different to yours as I found I blocked quite a bit talking to friends and family, but with strangers I would either start fluently then block more later in the conversation, or I would block horribly and literally be unable to form any sentences at all