What if you took the sashing out of the middle and just put the squares together with the seams offset? Or try a sashing strip that is not so busy. The polkadots seem to clash with your squares. 'Course, it could be one of those combos that doesn't seem to come together until you have a bigger chunk of it done. Just keep at it. Or put it aside for a couple of days and let the possibilities percolate in your brain a bit.