Are you using WD Sync? If so that is most likely the cause of a mysteriously full My Cloud. WD Sync keeps a “history” of files that are synced so they can be recovered if deleted. These are stored in a hidden directory on the My Cloud.
If you can access the My Cloud Dashboard, do so and enable SSH under the Dashboard Settings. Then one can access the My Cloud at the root/firmware level to see if the user files (Shares) still exist and one can remove the WD Sync hidden history files to free up space. The following post explains how one user recovered data hogged by WD Sync on the My Cloud.
If one reset the My Cloud via the reset button on the back of the unit, that will not remove user data files. However if one performs Quick Restore or a Full Restore through the My Cloud Dashboard, that WILL delete user data.
