From your post however, it sounds like you are using headphones (only) for your mixing. This can be very dangerous, and will not give you a true picture of your sound, or the stereo spread. Think about this:
You have 2 speakers on your stereo...each of your ears is hearing sound from *both* speakers, not just one. Albiet, there is a slight delay between when the sound from the one speaker reaches one ear vs. the other. This slight delay is what the brain uses to determine the position and distance of the sound. By using only headphones, you are losing all of this.
My advice, get yourself some decent monitors, and some basic room treatment, and hear the difference!!!
"Never interrupt your enemy when he is making a mistake" ~Napoleon Bonaparte~