I don't recognise the mixer model.
At a guess, you have the PlayIt Live main mix on 3/4 (perhaps via the USB) and take a mixed output from the main. You need to get the microphone gain set so when the mic fader is at the square box the meter lights flash to "0" or a little higher (occasional red).
Similarly you need to line up the music so it peaks to "0" then reduce the music to say -20 on the fader when you talk.
Listening on headpones plugged into the mixer that should sound fine if you do that. If the return to the computer is that mic/music mix from your mixer any downstream use (recording or stream) should be OK.
You will need to select your mixer in the "Audio source to broadcast" in the streaming encoder.and you should get the level so the indicator "wiggles" like your mixer meter.
Windows makes these settings hard to find sometimes, have a look in "control panel", "sound" and your mixer should appear there. You probably don't want to set either the output to the mixer USB or the input from the mixer USB as "default" but just select them as appropriate in PlayIt Live.
One revision to the above.
If I've identified the mixer correctly the USB isn't a sound card but a memory stick player.
Thus I'm sure you are using either the sound card in the computer or (more likely) an external card.
With that exception what I wrote above should be OK!
Thanks Mark i'v had to uninstall PIL And Reinstall It was the Asio plug-in
in advanced tab that was keeping my mic to be silent!! but i'm abot to install the beta version
so hope everything is still well
jay aubrey