@sarahsaffel "Ghost Touch" is most commonly caused by a failure of the digitizer and the display panel. Replacing the display assembly will most likely fix it. Remember that "has had some flex for a while" could just be enough to cause the failure of the assembly. The only other things is that you want to remove your screen protector, if it has one, and try again.
Of course you can also do a factory reset of your phone but make sure you have everything backed up and that you remember all of your passwords etc.
Since iFixit does not have a guide for this, use something like [https://www.youtube.com/watch?v=CNZbqOTaTV8|this video] to work on your phone.
While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.