Are you supporting the weight of the quilt? Is the quilt bunching up so it's not moving freely under the needle? My quilting area is very small and if the quilt bunches up against the back wall it doesn't move freely and my stitches are very small. (hope that made sense) I also use my ironing board to help support the weight of the quilt on the side by me so there's no extra tension or pull on the quilt. This also affects the size of my stitches.