first off, bullshit that that's you son
second off, if you're having trouble getting out what you're trying to say slow down, think of the words before they come out of your mouth
whenever you're just sitting around right down series of words that rhyme together and try to make some sense out of them, tell a short story
that way later on you'll have that shit memorized in a way, one word will automatically make you think of another word and so on.. that way you'll really "flow" and not get caught up