That’s a really complicated and unique issue. It sounds like the majority of the time you have little or no disfluency, and it really only gets bad under high stress. What do you do when you have to make emergency alerts? Are you talking over a loud speaker kind of system? If you are do you just choke out what words you can, or is it the kind of thing where after a long blockage you can speak normally? If it’s the latter a common strategy is to begin speaking in your head with words you won’t say out loud and use those to lead into your actual speech. Like if someone has trouble saying their name they might think in their head *my name is* and then say their name like a fluid sentence with the first bit in their head. Hopefully that helps. Either way, if the problem persists finding a speech therapist could be useful. Hopefully there are good ones in your area.