The Ender Dragon won't die?

I'm playing Minecraft on multiplayer on Xbox 360, creative mode, and I went to the end, and I keep attacking the Ender dragon but it's health won't move? It went down a little and now it's stuck and won't go down at all anymore, I ended it's ability to recharge it's health, and it just won't move, am i stuck in the end? I don't know what to do

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