System picks up PC-sound as extra mic signal while in combojack

[Genesi5]

So, i have ASUS K501UX, it comes with combojack and Conexant SmartAudio HD auidosystem. I used to talk via built-in microphone, and about three weeks ago i've got a combojack splitter for mic and audio from China. After that, my pals and teammates began complaining that they can hear everything on my PC - gameplay, youtube, music, etc. I don't know how to make it NOT TO PICK PC sound, and at the moment i'm about to pull my hair off. Looks like it works like stereo mixer and mic combined, but stereo mixer is OFF.

What could it be? How can i solve this?

 

[Genesi5]

MERGED QUESTION
Question from Genesi5 : "System picks up PC-sound as extra mic signal while in combojack"

So, i have ASUS K501UX, it comes with combojack and Conexant SmartAudio HD auidosystem. I used to talk via built-in microphone, and about three weeks ago i've got a combojack splitter for mic and audio from China. After that, my pals and teammates began complaining that they can hear everything on my PC - gameplay, youtube, music, etc. I don't know how to make it NOT TO PICK PC sound, and at the moment i'm about to pull my hair off. Looks like it works like stereo mixer and mic combined, but stereo mixer is OFF.

What could it be? How can i solve this?