Does your machine have the ability to mirror image a stitch? I think you want to use a different stitch mirror-imaged. It would help if you could post a link to your exact model so we could see your stitch options, as they can be numbered differently on different machines.
When you say a back stitch, you mean it takes a stitch in reverse?
Edit: If you haven't already, I recommend taking a scrap piece of muslin and sewing out each of the stitches. If you find the stitch that you want but it is facing the wrong way, check your manual to see if there is a way to mirror image it.