Headphones being heard clearly during calls.

I've had this problem ever since I built this computer. Every person I call can hear what I'm listening to clearly. Some how my headphones are projecting the sound through the mic channel and I've disabled the stereo mix so I really have no idea what's going on. I'm running the ALC889 version of realtek on the Gigabyte Z68XP-UD3. Any ideas how to stop it doing this? It's starting to piss me off.