Make sure your backups are NOT being stored in device storage. same thing happened to me then I realized cwm recovery sends backups directly to devive storage UNLESS YOU specify for them to be sent to external sd card. Once I realized this I deleted my backups and ALL my device memory came back.then I backuped and directed it to go to external sd card NOT internal storage where it goes by default. So make sure this is not happening to you. If you suspect it might be the reason your internal storage reads full simply delete your backups and then check your internal memory. If that's what is happening next time you backup direct the backup to external sd card.hope this helps solve your issue.i know when my internal storage read full this is what was happening to me. best wishes
Samsung Galaxy S4, Tmobile variant, m919 rooted. Please press Thank you if ive helped in any way.