Iphone 5 volume randomly decreases on its own

i just noticed earlier that when typing a text message, the keyboard clicks were almost totally silent. i checked the volume rocker, it was at full volume. i also noticed a little later that when playing words with friends, that the sounds in the game were also lowered and not at full volume. i again, checked the in game volume and regular volume and both were at full.

sometimes rocking the vibrate toggle or lowering and then increasing the volume fixes the issue and puts it back to full. anyone else ever have this happen?