If you say the shahada are you a muslim then? I heard even people who don't even mean it become muslim as long as they don't worship anything else.
Jazakallahughair.
:wa:
Merely saying the shahaadah dose not make a person a Muslim. There are certain conditions that have to be met in order for the Shahaadah to be valid, eg knowledge of it's meaning, full certainty of what it means without doubt, total acceptance of what it means etc.
So, if a person says it without meaning it, that does not make them a Muslim, because it is something so serious. It is not a game. You have to mean it, and know and accept fully what you are saying, otherwise you are saying with your tongue what is not in your heart.
See the following links on the conditions for shahaadah: