"'Have faith in God,' Jesus answered."
It seems it is not the amount of faith that matters to Jesus nor even the quality of faith. It seems not to matter if you have strong faith or weak faith, unwavering faith or doubter's faith. Jesus does not say have unquestioning faith nor does he mention anything about the kind of faith. However, the only thing that is important is the object of that faith, God.
Jesus says that even if you had faith as tiny as a mustard seed (that is not much faith at all), you could command mountains to be hurled into the sea. Nothing would be impossible for you. But why? It is because of faith's object, God, who is able and mighty to act, for whom nothing is impossible, that faith is so powerful, no matter the amount or the quality. Even he who has minuscule faith is secure because he stands on the Solid Rock of Ages. It does you no good to have strong faith that you will not fall if it is based on that which cannot last. Such a person is insecure despite believing they are secure. Weak faith in God is better than strong faith in the World.
Even if you are unsure if God is really there, he is the only one who is Eternal. Even if your confidence is wavering, trust in Him who does not waver and whose constant mercies are made new everyday.