What is the ruling on one who committed an act of disbelief (kufr) and apostasy (riddah) while ignorant of its nature, then repented, and subsequently became afflicted with obsessive doubts concerning apostasy, and cannot recall the last time he uttered the Two Testimonies (Shahadatayn), and whether it was before or after the act of disbelief?

You must increase faith, piety, and good deeds, and completely turn away from the whispers of disbelief and its details. The judgment of disbelief is not light, and whoever's Islam is established with certainty is not removed by doubt, and not everyone who falls into disbelief has disbelief befallen them. Scholars have stated that a Muslim is not excommunicated if their action could be interpreted as apostasy or otherwise, and if there is one way to keep them in Islam, while ninety-nine ways point to their excommunication, then that one way should be acted upon, in accordance with the hadith (definition): "Avert the prescribed punishments from Muslims as much as you can."