Strorage capacity problems with iPhone 4s?

I have an iPhone 4s which has a total storage capacity of about 13 GB. I do not have many apps, and often get the warning that I can't take pictures or download more apps because I do not have enough space. When I go to manage my storage, it says 6.0 GB is taken up by messages, even though I do not have ANY messages. What is this and how can I fix it? I often times have to delete pictures and apps to make room for something else, when I really do not have many pictures or apps at all. Any help would be great!

Have you tried restarting your phone? That usually works all the free space is now accurately measured.