I think I understand what your problem  is but I am not enough acquainted with
Excell vba  to be able to really help  you.
I can only point you to a direction.
.
If I understand you correctly, you want to find out what is the last row  with
data in your sheet and add  a new row from there.
You are using the used range.rows.count to give you the number  of used rows.
For some reason you are beginning your currentRow as number 5.
But what happens if the first 4 rows  are empty... Then your usedRange.rows
count will begin from row5 to ...
So first of all you should check whether row4 is empty  and not row5
If Sheet1.Cells(4, 1).Value = "" Then
but then again what happens if row4 is empty but not row 3 or 2 or 1.