Funny half screen problem

Question

I do not know the origin of the problem, but my television has been working great until recently. Now when I turn my television on I can only see the upper half of the screen and the shapes are distorted (people appear to be like midgets). The bottom half is black. The wierd part is that the upper half gradually gets bigger and bigger pushing down the black part and over maybe about 45 minutes I am able to watch the TV full screen or maybe with a half-inch left on the bottom. What is happening and is there a way (ie setting to change) to fix this?