PS3 controller on pc problems

[gardaringi]

I just recently started using my PS3 controller on my PC to play Dark souls 2. I downloaded the SCP system and at first it worked fine and I had no problems. Then it started disconnecting when I turned off my computer and I fixed that bit myself. Now the problem I keep getting is that while in-game, whenever I press the start button, I alt-tab, and the left analog button changes the song on my spotify. In other words the controller starts to act like a mouse but not a controller and I have no idea how to stop it.
I have Windows 10 and run it on fullscreen. If anyone has any idea how to fix this then I'd be very grateful.