What is the ruling on one who forgets to recite al-Fatihah when he is a ma'mum

The questioner : All right, the second question, Shaykh. If I finish reciting al-Fatihah with the imam, and I am a ma'mum in the prayer where the recitation is loud, and I forget to recite al-Fatihah, do I go back to the prayer?

The Shaykh : But you add a rak'ah in place of the rak'ah in which you forgot to recite al-Fatihah.

The questioner : Shaykh, what if I recite it twice in the same rak'ah, al-Fatihah?

The Shaykh : Why do you recite it twice?

The questioner : Sometimes I say that I forgot and did not recite it, so I recite it.

The Shaykh : Perhaps you are one who has many doubts.

The questioner : May Allah answer you.

The Shaykh : Are you one who has many doubts or not?

The questioner : Not once, by Allah, I am confused; according to some times, I say I did not recite it and I recite it.

The Shaykh : Yes, but do you often doubt?

The questioner : Yes, yes, yes.

The Shaykh : Leave the doubt. If I am certain that I did not recite it, consider that you recited it.

The presenter : May Allah reward you with good, O Shaykh.

The Shaykh : May Allah bless you.