Maybe too much bulk with seams going one direction or not iron pressing your seams. Try pressing all seams open, with right sides together line up seam to seam. You can hold them together and kinda rub them back and forth between your fingers. You can feel a little bump when they match up. Pin at the seam not right to left. Also peek under it just to make sure it looks good. I would also pin at the beginning and the end. I hope this helps. :thumbup: :thumbup: