iPhone 6 lock button problem?

So uh, my lock button is kinda in the same position as many 5s users. Problem is, I don't have a 5s! I have a 6 and when I hear people lock their phones, I hear a nice, crisp sound when you press the lock button. No effort needed. However, on my phone, it's getting harder and harder to turn off by the day and I don't hear the crisp sound of the button locking, but I do hear it with the volume button. I'm sure it wasn't like this when I first got it. Can anybody find a reasonable explanation to why this is happening, and how can i fix it??