I have this problem as well and it seems to get me in huge messes at times. Like you said, I am intelligent, I know what I am talking about but I cant say it. I end up sounding like….I don’t even know. I have 2 serious issues that I have been trying to resolve for years. My daughter and I were taken advantage of very badly by (get this, a disability councilor) and a landlord. We are completely in the right but my communication gets so horrible that people don’t understand me or take me seriously. It gets worse and worse.