What is the evidence that Islam was not founded recently, and that the Qur’an was revealed 1400 years ago and preserved from alteration, and how did we come to know our Prophet Muhammad, may God bless him and grant him peace, and how did Islam reach us?

The greatest aid in getting rid of obsessive thoughts (waswas) is to completely disregard them, to engage in seeking sacred knowledge, and to frequently supplicate to Allah to repel these obsessive thoughts and doubts. Its effective remedy is to utterly disregard them. And whenever the one afflicted by waswas pays no attention to them, they will disappear, unlike someone who listens to them, for they will increase until they drive him to the brink of insanity. Waswas is from Satan, whose goal is to lead the believer into error. Al-Izz ibn Abd al-Salam and others mentioned that the cure for waswas is to believe that it is a satanic whisper, and fighting it earns the Muslim the reward of a mujahid (one who strives in the path of Allah).