Is it necessary to ask about every doubtful matter in prayer when afflicted with obsessive-compulsive disorder?

You must learn the rulings of purity (Taharah) and prayer (Salat), and what must be learned immediately. Learning legal rulings and asking about them is not a form of waswasa (obsessive whispering). If you learn what is necessary for you, then turn away from waswasa and pay it no attention. For knowledge saves one from waswasa and prevents one from giving in to it.