Suffering From Severe Upper Abdominal Pain

I suffer from severe upper abdominal attacks. They come on suddenly without warning. I get extreme pain in the lower back as well. After a couple of hours the pain moves into what I feel in my bladder area. These attacks come in clusters it seems, maybe a few over a couple of weeks, then nothing for a couple of months. I have taken Oxycodone to help relieve the pain, but they don t help very much. I end up vomiting and itchy after the initial upper pain. I am also loosing my hair and am easily fatigued. The pain will subside after several hours, but my abdomen will remain tender for one to three days afterwards. The pain does not come in waves it is constant and equivalent to child birth. I have had four natural births without complication. I am a 42 year old woman. This started in 2008 and was bearable then, but over the years has progressed into what it is today. G.I. has said it is irritable bowel, which i occasionally do suffer from, and is always relieved with a bowel movement. this pain stops on it s own and never is associated with a bowel movement. Almost always the attacks happen after 10 at night or before 10 in the morning, never through out the day.