Sometimes in the prayer I forget if I had recited Surah al-Fatiha or not. Therefore, I recite it a second time. Is this action proper? Should I then perform the prostration of forgetfulness?
Many people get numerous devilish whisperings during the prayer. This causes them to doubt if they had recited [al-Fatiha] or made the tashahud [and so forth]. The cure for that is to make sure that one really gets attuned to the prayer and the heart is fully conscious during it, fearing mistakes or devilish prompting. If that happens a lot and one usually recites al-Fatiha, then it is disliked to recite it again. However, if one does repeat al-Fatiha just to make certain and be on the safe side, then he does not have to make the prostration of forgetfulness.
Shaikh ibn Jibreen