Is a person considered doubtful in their religion and an unbeliever due to the whispering doubts about creed that drive them to research and read to strengthen their faith, relying on the saying of the Prophet, peace and blessings be upon him: "Indeed, Allah has pardoned my Ummah for what they self-whisper, as long as they do not act upon it or speak of it"?

You are not an infidel, nor are you doubting your religion. These whispers do not harm you nor affect the soundness of your faith. You must strive against them and seek to get rid of them. You will remain on good as long as you struggle against them. The proofs of Islam's validity and the Prophet's (peace be upon him) truthfulness are clear. We advise you to exert effort in learning, to associate with righteous people, to increase supererogatory acts of worship, and to supplicate for steadfastness upon the truth.