Mistake in gstr-3b returns

HI SIR, 

I have filed GSTR-3B for all the month upto date, now i found i have missed out claiming ITC of 3 to 4 invoices every month since Nov-17 to March-18, how can i claim credit. how do i rectify, please give a solution, Can i claim all the ITC in April -18 GSTR-3B Returns ??? Somebody please help me. 

My Mail ID - venkateshsulegai @ gmail.com