First of all, it's awesome to hear that you've made it successfully through those other challenges. Also, I definitely relate to the feeling of incompetence when you can't say what's on your mind, or your mind goes blank. The only advice I can give (because it helps me), is to let the person you're speaking know beforehand that you have a stutter/speech impediment. I find that when they're expecting disfluency from me, I don't stutter nearly as much. That openness seems to help me. Alternatively, writing an outline for what I'm going to say or points that I want to make helps me not to forget anything. Never a bad idea to organize! Best of luck :)