Why does my iPhone 5s never have storage?

My iPhone 5s has, within the past year, been causing me serious issues in terms of storage. It currently still has iOS 7, which I recently tried to update because I figured maybe that was contributing, but the update would never complete. Anyway, it is constantly giving me storage messages, saying it has no room to back up, etc, etc. I ve tried to clear space. I only have three apps on my phone at this point (deletable ones, I mean--there are of course the apps that you can t delete). I have only twelve pictures, only ten songs, etc. I ve removed all my pictures in the past and nothing has changed. I m losing my mind with this because it is making it so that I can t take photos, can t download apps, can t send photos etc. I ve tried googling it, but can t find anything that helps. If no one on here can help, my next stop is probably the apple store. Does any one know how to fix this?

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