Since loop() already loops indefinitely, I can't see that adding a while loop that way would help.
Here is the real issue:
if(index < message.length()) {
What happens when index equals message.length()? The code stops doing whatever it does.
If you want it not to stop, you have to reset index to some value. Find the matching }, and add an else clause in which you set index to 0.
Finding the matching } would be a lot simpler if you put every { on a line BY ITSELF, and properly indented your code (Tools + Auto Format makes that so easy...).
Delete the while loop that Chris had you add.