All perfect praise be to AllahThe Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
Al-Fatiha is a pillar without which prayer is invalidated,and whoever has doubt about having recited it or not takes one of the following rulings depending on their situation:
First: If a person doubted not having recited it at all, then he is obliged to recite it all over again.
Second: If he, before having completed its recitation, doubted having forgotten some verses, then he is obliged to recite it all over again.
Third: If a person, after having completed its recitation, doubted not having recited part of it, then he is free from liability.
In this regard, Al-Imam Al-Shrbini (May Allah have mercy on his soul) said (What means): "If a person doubted whether he had recited it (Al-Fatiha) or not, then he is obliged to recite it again because, in principle, he hasn`t recited it. Moreover, if he,after having finished recitation, doubted that he didn't recite some verses, then he is free from the liability, but if he hasn`t finished the recitation, then he has to recite it from the very beginning." [Mughni Al-Muhtaj vol.1/pp. 356].
Al-Hattaab, a Maliki scholar, said: "A person's continuous doubt as regards not having recited Al-Fatiha or part of it is considered an evil suggestions of the devil." [Bughyat Al-Mustarshdeen, pp.66]:".And Allah Knows Best.