Hi Emma,
We can give you the best answer possible if we can see what you see, so it would be most helpful if you could add a picture or two of your TV screen showing the problem to your question.
[guide|21499|Adding images to an existing question - iFixit Repair Guide|new_window=true]
That being said, it certainly sounds like the screen has suffered damage; stripes, black lines and splotches are typical symptoms of a broken screen. I would prefer to withhold judgement until we see pictures, but if the screen has indeed been cracked there's really nothing to be done about it. ***If*** a replacement display is available at all, the cost is generally more than what the television is worth; we've seen cases where the screen cost twice what the TV did originally!