iPhone 4s volume changes with music app functions such as shuffle and skip

Recently, I have been very irritated with my iphone's music playback because the volume is inconsistent. For almost every song, as it starts playing it will start at a normal volume then decrease suddenly to a common level. It sounds like the volume difference created by sound check. Besides this, doing things such as skipping, turning shuffle on/off, turning repeat on/off, and other minor things will change the volume. the most notable is skipping, which reverts the volume back to the loud version (as if sound check was off), while turning shuffle and repeat on/off only changes the volume slightly (barely noticeable unless playing at a loud volume). I have tried to ignore it for all this time, but now it is just annoying. it would be nice if apple had a simple email contact option to ask questions as well, but apparently they either don't or it is impossible to find, and that ****** me off even more.