Anyone who does not occasionally worry that he may be a fraud almost certainly is. Nor does the worry absolve one from the charge; one may still be a fraud, just one who rightly worries about it on occasion. Likewise, anyone who does not occasionally worry that she is wrong about the existence or nonexistence of God most likely has a fraudulent belief. Worry can make the belief or unbelief genuine, but it cannot make it correct.
This type of humility regarding your beliefs is exactly what is missing from our public discourse.