Try moving your mailmerge above the for loop and then step through each record set inside the for loop:
With wdDoc.MailMerge
.MainDocumentType = wdFormLetters
.Destination = wdSendToNewDocument
.SuppressBlankLines = True
With .DataSource
.FirstRecord = wdDefaultFirstRecord
.LastRecord = wdDefaultLastRecord
End With
.Execute Pause:=False
End With
For x = 1 To nRows
With ActiveDocument.MailMerge.DataSource
.ActiveRecord = x
If .ActiveRecord > .LastRecord Then Exit For
End with
'.... rest of your for loop