I'm sorry they haven't done more for him.
My son is completely nonverbal he does use AAC but is not always reliable. He is a fairly reliable pointer though. I at first tried the traditional black and white pain scale but because of his vision impairment he had difficulty reading it so I found this pain scale on the internet that used bright colors to rate pain and he can read and point quickly to where he is on the pain scale. Here is the one we used;
It is called a Visual Analog Scale.
It sounds horrible but when he first was Rxed the Coedine I started to refuse to administer pain medication unless he indicated in some way he was in pain. We started out simple "you want mommy point to me or if you are in pain and need something to make it go away point to the medicine bottle." It resulted in a few tantrums during pain bouts but I felt it was important to teach him he has to communicate his pain.
We are slowly progressing and refining his pain communication. Now he is good at pointing up if he has pain in the bony area of his chest (reflux) or pointing downwards if he has pain in the soft area of his belly(lower GI pain). The analog scale was something we only just started to do in the last few weeks so now I have his input into how severe it is instead of just observing and rating it myself based on what I see. Although I will say when his pain is off the charts severe his communication regresses severely and I can only get a point at the Rx bottle response.
Any way this is what has worked for us, every special needs child is different and what works for us might not work for you. It was a long process of over a year just to get him to communicate that much and I am still working out ways to refine the communication technique.