Impaired functionality on trackpad, mouse and keyboard.

None of the gestures requiring two or more fingers are working on the mouse or trackpad. I can't even double click (which I have set for two fingers).

Some of the keys on the keyboard are also not working properly - e.g. when I press my volume down button, the screen switches to the desktop. Can anyone help???

I can't seem to find any suggestions on the forum for what to do when all three items are working improperly - must be a software issue since they all went wrong at the same time?

Thanks in advance for any help you can offer!