Enderdragon messed up in Minecraft 1.5.3

I tried to fight the enderdragon in my survival world and it messed up. At first everything about the End was normal but after about destroying half of the crystals the enderdragon suddenly dissapered!!! The portal to the other world then came lit and I was able to go back to my base. But when I went back to my base I walk a few distances ahead of it then I saw the enderdragon in the other world!!! I was so nervous that I would lose important stuff I created but the enderdragon flew of in the sky!!! I tried and respawn the dragon and again at first everything was good but this time I destroyed every crystal and was preparing to attack the dragon. This time the dragon came to the center and stayed there. I tried to hit it but it didn't take any damage. Again the portal had lit up and I managed to go back to base. Luckily this time the enderdragon didn't appear in the other world again. And also I didn't get the dragon egg...