I sound so unbelievably stupid when I speak

I sound so unbelievably stupid when I speak there is an enormous contrast between my thoughts and the words I utter. Someone will say something to me and I will come up with a response almost instantaneously in my head, but when it comes time to say it, I block uncontrollably. So much so that I need to swap words and basically restructure my entire response, which more often than not just leads to it being a jumbled incoherent mess. I envy people that just let words flow from their mouths with ease. I just can’t even begin to imagine how easy life would be if I could speak so gracefully. No one, and I mean no one, so much as shows me a modicum of respect when speaking. While I don’t care much about other people and what they think, it would be nice to be taken seriously every now and again