If your quilt has shifted that dramatically, I would definitely rip the stitches out (I know that can be painful after all that work), then purchase a walking foot if you do not already have one. I could not have quilted all the larger quilts I've made without one, it will make it so much easier all the way around. I have done twin size quilts with just squares, then I used a semi-short zig-zag stitch starting at one corner, then moving over to the next square and do the same until you need to switch the quilt to stitch in the other direction; which makes it so much easier.