So sorry you too have GP. I have had many tests recently and found I have digestive tract paralysis...which includes gastroparesis, a stomach that no longer stretches and can't handle more than 10 ounces of fluids, colonic interia and pelvic floor dysfunction.
Pain is a big part of GP for many.
I would suggest getting a motility specialist involved in your treatment. Also on facebook there is a great support group called G-Pact. If you look up G-pact online there is tons of info about GP and DTP.
I have been battling with this for over a year now( was diagnosed in 2008). Down 50 pounds so far and on a strict diet ordered by my motiltiy specialist.
It can be very difficult to treat. Some do get better though so hold on to that.
I am here if you need to talk more...firstname.lastname@example.org.