Is one who oscillates between two fatwas, one that warns against using phrases that involve impudence towards God and considers them disbelief, and another that does not, especially since the questioner suffers from obsessive-compulsive disorder, sinful? And is following different fatwas considered heresy?

Adab (proper conduct) with Allah the Almighty is required, but not everything that infringes upon it constitutes disbelief (kufr). The word "Rabb" (Lord) is used for Allah and others. The phrase "leave the Lord of the pens" is understood according to its context. The default state for a Muslim is to assume the ruling of their Islam, and one whose Islam is established with certainty is not removed from it by doubt. A person is not declared a disbeliever except when the conditions for declaring someone a disbeliever are met and its impediments are absent. The questioner's hesitation in acting upon two different fatwas is not a blameworthy pursuit of concessions; rather, it is permissible for them to take the easier opinion, considering their situation, especially for someone experiencing obsessive thoughts (waswas (definition)). There is nothing mentioned by the questioner that necessitates asking about falling into disbelief. Asking multiple scholars is not heresy (zandaqa); heresy lies in seeking out the slips of scholars and the concessions of jurists, not merely in asking more than one scholar.