Looking at your photo...it reminds me of my first quilt...
So - one question... Once you cut the blocks, did you then stitch a row, then the next etc, and then did you connect the two rows?
I made one similar to yours - and didn't know about strip piecing, or creating the quilt in rows...
and - as everyone else says... that blasted 1/4 inch seam will get you every time...