Vent kinda? More so rant but still

I feel like I talk to myself so much in my head about so many different things and I have so many opinions on a million different topics but the moment I actually get a chance to voice them out to someone the words refuse to leave my mouth. I will literally have a speech repeating over and over and over in my head but I cannot for the life of me speak it into existence.  It irritates me so badly. I think a big part of it is that I have horrible social anxiety but the thing is that it's not even with strangers or big crowds, it could literally be me in my bedroom talking to my bestfriend and it still will not come out. When it does it comes out stuttered mumbles and it's so embarrassing.  I could type what im thinking no problem I do that alot, mostly on my Tumblr but soon on this account aswell.i can think my thoughts,  type them,repeat them to myself in a quiet room a thousand times but stilling just will not come out correct the second I'm with someone. The moment I am speaking up it's like all of a sudden I cant control my voice. Things come out completely wrong, my grammar becomes horrible and my voice gets all wishy washy and quiet. It makes look so stupid and like I have no clue what I'm eve trying to say. Half the time my friends just cut my off with: "Yeah no i get it" when i KNOW they don't and they just don't wanna hear my nonsensical ramble for which I don't blame them, but it just makes me feel more like an idiot. Ivebeen I and out of speech therapy my whole life and it hasn't ever helped whatsoever not even a little bit.  My whole life I've been told by my teachers I have amazing writing when it came to essays or writing work. I know what I want too say, why can't it just come out of my mouth :[ 

Sorry if my punctuation and or grammar sucks in this im really tired and just needed to get this out of my brain for tonight.