Are obsessive doubts concerning religion and the methodology of Ahlus-Sunnah wal-Jama'ah, which are faced by a person afflicted with OCD, considered a departure from the fold of Islam, and how can certainty towards the methodology of Ahlus-Sunnah wal-Jama'ah be strengthened?

What you find within yourself of waswas (whispers/obsessive thoughts), its cure is to completely disregard them. Increase your participation in gatherings or listening to the words of scholars in faith-building and admonitory lessons that strengthen imaan (faith). Avoid being alone with yourself, and associate with righteous, upright women who follow the Sunnah (definition) (Prophetic tradition) and possess sound aqeedah (creed), as they will help you adhere to your religion.