I havwe been quilting off and on for about 2 years cuz of the hours I work. I'm working on a quilt now that has alot of 2 1/2 inch square. I have attached most of the rows, now im on the last 4 and one row is not matching up with the others. i measured the squres and they are 2 1/2" wide by 2 1/2. What am I doing wrong. I'm a perfectionist when it comes to matching seams. HELP!!!!!!