Offer a humid hide either always or at least when he is about a shed. Or if you have it in an aquarium then humidity could be escaping (especially if you're using a heat lamp), which would explain bad sheds (when a snake freshly sheds if you pick it up it should be soft and you should be able to unroll it without breaking it, etc).
Just bump your humidity up and everything should be fine.
Err... ~_~ or instead of bumping the humidity try offering a humid hide. If your humidity was in the 70s then everything should be fine.