haunted ringtone/text message ringtone?? helpp pleaseeee

Ok I have no idea why, but my phone decides to change its ringtone to whatever it feels like WHENEVER it feels like. I went into my "modes" and settings > sounds and changed my ringtones every time and it still changes on its own and its a different song every time. When I receive a text it plays chris daughty's "home" even though I changed it in the settings and it says so in the settings even wen it still plays that. Its really driving me completely insane lol. I recently put a ton of music on my SD card but I don't know why its doing this all of a sudden. Pleeeease help!!!!!