iPhone strange sound problem

When I press the buttons on the side of the phone, for the volume, it doesn't change but it displays the ringer with the speaker icon, but the sound doesn't go up. It IS on ring, not silent. The sound does work, because when I adjust the sound in settings, it does play my ringtone as to show you how loud the phone is at that setting. However, no other apps can play sound, how do I fix this?

EDIT: Also when i'm on youtube or whatever, it doesn't display a volume bar at the bottom. Theres just the play buttons and whatnot.