Why does my iPhone screen click when I press on it?

It's my front screen that does this, I have an iPhone 4S and I got it a little less than a year ago, I've dropped it quite frequently but it has no cracks, I have a front screen protector and used an otterbox for a long time and lately I've been going without a case and have dropped it about 3 times and luckily none of these resulted in anything more than scratches and little chips to the borders of the glass. Anyways, when I press on the front screen, with more pressure than a tap, it clicks, like I'm popping it into place or something but it continues to do this. Everything else on my phone is working fine though. Should I be worried? Is there something wrong with it?

Well there are two possibilities.
Either A. You activated the 'make a noise when I press the screen' option and don't remember or
B your screen is separating from the rest of the phone, and it will be broken soon.

You NEED to put it back in its case!