iPhone 4S sound won't work, option disappeared?

I've had my iPhone for a few months now and had no problems with it. About a week ago the sound began to randomly turn on at off for no reason. When I use the buttons at the side it just comes up as "ringer" but the actual volume bar isn't there. My music and videos won't play and I have no sound when I receive messages and calls. Its not on silent and it's the hold button isn't on. The only way I can get sound to work is to go into settings for ringtones and that's the only time I can get any sound from it. In Settings the same won't work for message alerts or anything else, only ringtone sound for some reason. Is there anything I can do to fix this?