iPhone 4 No volume icon, unresponsive volume controls, no sound in apps

My iPhone 4 recently, and suddenly, has sound issues. The volume icon does not appear when the volume buttons or slide bar are pushed. As well, the volume buttons do not increase or decrease the sound. There is no sound when my text tone should be played. My volume bar still appears in Music and Youtube, but I do not have sound from any other apps. My speakers are functional. My ringer and alarm still sound.

I did not drop it in water.

I have blown into the headphone and charger port.

I have cleaned both the ports with a clean toothbrush.

I recently updated my software to iOS 7.0.4 and bought/used a non-Apple brand iPhone charger.

I am technologically challenged and would very much appreciate help!