Monitor distortion and click recording unintentionally

I’m having an issue with my setup

Mixing desk: Yamaha MW10c USB Mixer
Cubase Elements 8

I am able to record with monitoring off.
I am able to playback.
When I turn on monitoring there’s a buzzing sound that starts and escalates.
If I press down a key on my digital piano when monitoring is turned on it reverberates really fast and distorted.
If I turn my click on while monitoring is on it it does the same thing.
If I record with monitoring off and the click on I record my piano AND the click!

I have not had this problem ever before and have regularly recorded using a click track. Everything was working fine a month ago with the Cubase Elements 8 trial, but I bought the full version and have encountered this problem. I don’t think my problem is to do with upgrading though as I have AI5 installed and the issue is happening with AI5 also and was happening before the upgrade. I did upgrade thinking it would fix my problem, but that’s the way things go.

A bit stumped as to what the issue is. I have uninstalled and reinstalled the most recent driver for my mixing desk.

Any help would be really appreciated! I’ve been looking through forums for a good few hours trying to find an answer, but so far nothing has fixed it.