I free up space on my iphone but in a matter of minutes my available storage is once again 0 bytes

[iPhone 4S 32GB - 28.2GB available]

My phone has been telling me that my storage is either almost full or full CONSTANTLY for the past few months. I delete a few hundred photos and some apps to free up space (I have very little music on my phone but I think I will remove these tonight), I then check my settings to see how much space I have freed up e.g. 100mb but in a matter of minutes it will go back to 0 bytes available and I don't know why. Because of this, I cannot update the OS so atm it is still on ver 6.1.3 (old, I know.)

I do not have icloud or photo stream turned on.

Please help! This is so irritating!

Thank you in advance.