Galaxy S5 :: Why Doesn't Phone Turn Off When Get A Notification On Lock Screen

Why doesnt my s5 turn off when I get a notification or when I check the time On lock screen. This been happening for the past days. I had about 55% of battery and when I got off work it was dead. I then later charged my phone and noticed that when I get a notification on the lock screen it won't turn off right after the notification showed. when I turn on the phone to check the time on the lock screen it doesn't turn off. it would usually turn off seconds later. This has been draining my battery. if I have a full battery at night and disconnect it and throughout the night I get a text message the lock screen would turn on and never turn off,and then in the morning I'm left with a dead phone or a 3% left, or when I disconnect the phone it doesn't turn of neither. How do I set it back to how it was. I already factory reset?