My car speaker is acting really weird?

Ok, so I drive a 2010 Mitsubishi lancer and whenever I play music through the radio, the speakers work perfectly fine. Absolutely no distortion what so ever. When i try to play music through my CD player, the left speaker gets faint and so the right speaker is louder then the left. When I equalize all the sound through the left speaker, the music playing is just really fuzzy and faint and when I switch to the radio the left speaker is fine. I have no idea what could be causing this, can anyone help me out?