What is wrong with my screen?

I've had my 5s for almost three years as of now, as so far I had had no issues. But, after no noticeable event I've started having issues with my screen: I'd take the phone out of the pocket, unlock it with my fingerprint, and then, when I went to use it, the screen did't respond at all! I could not swipe or open anything, even though the LCD was fine and I could still see the phone was working. In the beggining I had two ways out of it: Force restarting the phone or, weirdly, pressing really hard on the screen-to the point where the point I was touching got blurry- which make, suddenly, the screen to be responsive again.

As of yesterday, the problem got worse, as it is more frequent and the only way to fix it is to restart the phone several times.

For the experts out there, what could my problem be? I've had dropped my phone sometimes, but always with a case. Should I be replacing some internals? And what exactly?

Thank you for the colaboration with a non-native english speaker :)

Edit: I already restored my phone on iTunes and it did not fix it :(

More feedback on what is going on!

I have restored my phone and set it up as new but the issue wasn't fixed.

I installed the iOS 10 GM as I was afraid it could be something on 9.3.5 but, for my despise, it wasn't.

Therefore, I assume it must be something hardware related. I noticed that it happens more often while I'm moving and the phone had been on my pocket or on my bag. After several force restarts on the phone standing still it starts working again. Any tipson what should I look inside the phone or replace?