Have your tongue ever been cramped during oral 5ex? only then can u know its not funny as it may sound.
You can strengthen your jaw and tongue muscles by doing push-ups. Push the underside of the tip of your tongue into the front of your hard palate (the front of the roof of your mouth, right behind your front teeth). Do this more often and with strength then you will become use to.
In order to take this exercise to another level, you can try putting hard-shelled chocolate between your tongue and the hard palate and crush them with your tongue.