Shed cycles are far more difficult to see the signs of in white snakes...now you know.
Best way that I confirm whether or not a snake is in shed is in a DARK room, use a tiny flashlight & shine across the arc of snake's eye...this shows if it's milky or not.
Often their tummy scutes appear to have a double-edge too, when you look close.
If you just found new pieces of shed & he's "crinkly" it's a pretty good bet that you missed the signs...what's his humidity now? Have you raised it?
Everyone makes some mistakes with snakes- it even rhymes , just concentrate on what he needs...you'll learn to trust each other, with any luck.