He used not to recite al-Faatihah behind the imam; should he repeat those prayers?
Question

                have been praying behind imam for about three months withiout reciting Al fatiha,following enough and sound evidences from hanafi school.now I know the weakness of the hadith ,I ask if I should make up all those prayers.if yes ,I have an holiday in June ,I will have plenty time ,can I make them in june?
Praise be to Allah.
    
    Firstly: 

    
    With regard to the worshipper reciting al-Faatihah when he is praying behind 
    the imam, this is one of the issues concerning which there was a difference 
    of opinion among the scholars (may Allah have mercy on them). 

    
    Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: The 
    (scholarly) opinions boil down to three: two opposite views and one in the 
    middle. One of the two opposite views is the view that he should not recite 
    behind the imam in any circumstances. The second view is that he should 
    recite behind the imam in all circumstances. The third view, which is the 
    view of the majority of the early generations, is that if he can hear the 
    recitation of the imam, he should listen attentively and not recite.

    
    End quote from Majmoo‘ al-Fataawa, 23/265 

    
    The opinion followed on this website is that reciting al-Faatihah is 
    obligatory for the one who is praying behind an imam both in prayers in 
    which the recitation is done quietly and those in which it is done out loud. 
    This has been explained in the answer to question no. 
    10995 

    
    Secondly: 

    
    If a person does not recite al-Faatihah following the opinion of a scholar 
    who says that it is not obligatory, or he does not do so because he is 
    unaware that it is obligatory, there is no blame on him and his prayer is 
    valid. 

    
    Shaykh Ibn Baaz (may Allah have mercy on him) said: If he does not recite it 
    – i.e., al-Faatihah – because he thought that it was only required of one 
    who is praying on his own or the imam, or because he was unaware of the 
    shar‘i ruling, then his prayer is valid, because he did not deliberately do 
    something that Allah has forbidden or omit something that Allah has made 
    obligatory; rather he did not do it either on the basis of what he thought 
    was correct or out of ignorance of the shar‘i ruling. So in this case his 
    prayer is valid. But in the case of one who was aware of the shar‘i ruling 
    and believed that it was obligatory upon him, but he omitted it 
    deliberately, this renders his prayer invalid, because he went against what 
    he believed and he went against what he knew to be the truth.

    
    End quote from Fataawa Noor ‘ala ad-Darb, 12/344 

    
    Based on that, you do not have to make up the past prayers, because they 
    were valid. 

    
    And Allah knows best.