I am working on a BOM and made my first block this past weekend. Everything went together well and the block turned out great, however, when I measured it, it was 1 1/2" too small. The block was supposed to be 12 1/2" square and mine is only 11" square! I don't know what happened! I even measured the space between my needle and the edge of the presser foot to be sure that what I was sewing was a 1/4" seam. I can't find anything wrong. Can someone help me with another way to check to be sure I am sewing the correct 1/4" seam?