Do you preWash your fabric? I did not used to, but once I had a fabric that I cut accurately but steam pressed them before sewing them and after they were pressed the squares didn't fit my other pieces. I finally measured them before and after pressing and my 8" squares had shrunk to 7 3/4"! Likewise after sewing two pieces together it it easy to iron them out of shape if you are heavy handed with the iron vs 'pressing'.