Touch-pad Left Button Turns Off Computer

I have an XPS15 and recently have noticed that after it's been on for a while I try to click the left button on the touch-pad and when I do the screen goes to black and although it doesn't turn the laptop off completely it's as if it's in a sleep state. The lighted keyboard goes black but the power button stays lighted but then flickers then goes to black. If I then click it, the computer "wakes up" goes to the blue screen with the small square Dell logo with "locked" "switch user" option. When I click on the logo it'll sometimes go back to the screen where I once was, but if I click the left button again to continue it'll turn off again.

This seems to happen most of the time when I'm playing a game, although it just happened again when I was writing this. I haven't noticed it when I'm doing an email. I have also experienced it "going to sleep" when I'm very close to the left button but NOT touching it. The whole pad seems to be very sensitive and even turns words blue (as if I were highlighting), and even switches pages without a command from me.

Any ideas would be very welcomed.

Thank you,

BarbB