if(myBluetooth.available())
{
myBluetooth.println(str);
}
What is happening here?
Do you expect to receive something from an external source via the Bluetooth Module? myBluetooth.available() method is used to check that if any character has arrived at the receiver section of the BT Module and then byte x = myBluetooth.read() instruction is executed.
It looks like that you are writing to the Module (myBluetooth.println(str)); then, why have you executed the myBluetooth.available() method?