Headset Sound Issue

Hi everyone,
I am using a Tritton AX180 headset for both sound and voice and I'm having a few issues. Originally, I used Logitech speakers for the aircraft sound and just the headset for mic but now I no longer have speakers I am trying to use it for everything. My issue though is that while in the aircraft I can't hear any noise except the engines. For example on approach, I no longer hear "50, 40, 30, 20, 10" or the noise of he fmc buttons, or dials. Does anybody have any clue to this? And while on the topic of sound, the only reason I am having to use my headset for both sim sound and mic is because for some reason, my Asus monitor refuses to play any sound at all. I don't know why.

Help is appreciated,

thanks.