As rough as this post may sound to some, it's absolutely correct in that you are in essence wholly responsible for bettering your fluency. Even if you don't want to make the shift to extrovertism, you can still do something.. Read poetry out loud. Figure out your typical syllable obstacles and work on them. Call your friends on the phone and practice. Your impediment is like an instrument. I've learned how to even use it to my advantage (Asian girls love it c; ), and I've learned and practiced how to concentrate on my fluency. You can to. Start your practice today.