What do you mean by waking up? When you get a push message, toast, text or alert, the screen will turn on for a few seconds and then go black again. Being capacitive, a case or you pocket (unless you hand is in it) will not keep the screen on. So no worries. That's why you need to slide the lock screen to unlock the phone.
Did you change anything thing in Sound settings where you are now getting these wakeups?
Sent from my HTC Surround using Board Express