Hello there.
Are you diabetic? That is the number one cause of gastroparesis, as I have been informed. I do not have this, but understand your frustration. pain and stress. I too suffer from GERD and have been on Protonix for a number of years. This drug has been helpful to me. Perhaps a food diary would be of help to you. I had to start one after being diagnosed with bile duct dilation, and was surprised at the number of foods that I like but can no longer tolerate. For example, no peanut butter, but almond butter. No dairy except Greek yogurt etc. I too was diagnosed with ulcerative colitis, or rather microscopic colitis. I understand how awful this diagnosis can have an effect on you.
As for stress, have you tried deep breathing. I take klonopin when I need it for my anxiety, and it too has been very helpful to me.

I wish you luck in getting the care you need that will enable you to live a fuller life free of pain, stress and everything else. Our stomachs can often be the holder of all of our emotions/feelings, and naturally our stomachs get upset when we are under a great deal of stress, like you seem to be.