What should I do about my constant doubt concerning the number of rak'ahs: did I pray four or five?

One who experiences frequent doubt in prayer, to the point where it becomes like obsessive whispers (waswas), should not pay attention to it or rely on it. This is because it leads to a kind of obstinacy and results in adding to the prayer. Instead, he should perform the prostration of forgetfulness (sujud al-sahw) after the salutations of the prayer. According to the Maliki school, the criterion for frequent doubt is its occurrence every day, even if only once. The preferred approach to dealing with frequent doubt is to disregard it and build upon what is most likely correct, in order to alleviate hardship and difficulty.