Merge Sheets Within One Workbook

I'm working on a spreadsheet and need to write a macro that at the end of the day will summarize all the other sheets. I want the summary sheet to refresh each day and I also want the sheet to be linked to a pivot table that will refresh off of the new summary sheet data.

This is what I have so far. It summarizes all the sheets into one sheet, but creates a new summary sheet each day instead of just refreshing the sheet like I want.

Option Explicit

Sub Merge_Sheets()
    ' Takes every sheet in a workbook and pastes everything into
    ' one sheet (only copies headings once)
    
    Dim mergedSheet As String 'Hold the name of the new sheet created
    
    ' Insert a new worksheet at the beginning of the workbook
    ActiveWorkbook.Worksheets.Add Before:=Worksheets(1)
    Dim sameNameCount As Integer
    sameNameCount = 2
    Do
        If Not WorksheetExists("Summary") Then
            ActiveSheet.Name = "Summary"
            Exit Do
        ElseIf Not WorksheetExists("Summary " & sameNameCount) Then
            ActiveSheet.Name = "Summary " & sameNameCount
            Exit Do
        Else
            sameNameCount = sameNameCount + 1
        End If
    Loop
    mergedSheet = ActiveSheet.Name
    
    ' Loop through each sheet, copying each
    Dim wksht As Worksheet
    For Each wksht In ActiveWorkbook.Worksheets
        If Left(wksht.Name, Len("Summary")) = "Summary" Then
            GoTo nextWksht
        End If
        
        wksht.Activate
        If Worksheets(mergedSheet).Cells(1, 1) = "" Then
            ' Fill in headings
            Range("A1:I1").Select
            Application.CutCopyMode = False
            Selection.Copy
            Sheets(mergedSheet).Activate
            Cells(1, 1).Select
            ActiveSheet.Paste
        End If
        
        wksht.Activate
        Range("A2:I" & wksht.UsedRange.Rows.Count).Select
        Application.CutCopyMode = False
        Selection.Copy
        Sheets(mergedSheet).Activate
        Range("A" & getNextEmptyRowInSheet(ActiveSheet, 2)).Select
        ActiveSheet.Paste
nextWksht:
    Next


End Sub





 
Public Function WorksheetExists(WorkSheetName As String, Optional WorkBookName As String)
     
    Dim WS As Worksheet
     
    On Error Resume Next
    If WorkBookName = vbNullString Then
        Set WS = Sheets(WorkSheetName)
    Else
        Set WS = Workbooks(WorkBookName).Sheets(WorkSheetName)
    End If
    On Error GoTo 0
     
    WorksheetExists = Not WS Is Nothing
     
End Function

Function getNextEmptyRowInSheet(sheet As Worksheet, testColumn As Integer) As Integer
    Dim row As Integer
    row = 1
    
    sheet.Activate
    
    Do
        If Cells(row, testColumn).Value = "" Then
            getNextEmptyRowInSheet = row
            Exit Function
        Else
            row = row + 1
        End If
    Loop

End Function

Thanks for the help!!!

-Christina