You need to clear out the history and cache from Facebook, Safari and so on. If you go into Settings and go thru all your apps and delete cache and history on all of them it should clear out some of that. Then there is your messages, your texts and so on. Clean that out as well.
This could help you but this will remove all your saved data and media from your phone. (1) Turn it off and then hold Volume Down and Start the phone, keep holding the the buttons. (2) Now you will come into to recovery menu. (1) Use the Volume keys in order to navigate through the recovery menu. (1) Select “advanced” and choose “wipe dalvik cache”. (1) Return to main menu. (1) Then select “wipe data factory reset”. (1) Return and this time choose “wipe cache partition”. (1) Return and select “reboot system now”. (1) Your handset should start in Android OS now