I don't known what you've gone through but it makes sense that you wouldn't be able to talk in similar situations. I'm obviously not an expert but it would make sense for you to enter fight or flight and for you body to seize up. The best explanation I've seen for speech blocks is you do a valsalva maneuver in order to stop you breathing for example your in a jungle and a tiger walks by you your body freezes and you stop breathing so the tiger can't hear you. If you were in some sort of terrible situations when you were younger maybe now you have that same response in those situations now