Why does my iPhone sometimes dont respond

I have a 6 Plus that i’ve been using since launch in 2014. About a week ago i was using it normally when suddenly started to press something in the screen. It was the original screen from the box not a replacement. At the time i didn’t think of anything and just restarted the phone and fixed it. A few days later it started to not respond to touch. I put the display to sleep and turn it on it works again and repeats about every 5 minutes. Now it doesn’t respond at all. I was about to buy a new screen but decided to ask first as i think it might be a software problem as it started happening after i updated to ios 12.5.1. Do i need to change my screen?