Abdominal pain spreading to the back

Sandra - 60 years old

diagnosed with Restless Leg Syndome
medication - taken at bedtime:
Sifrol (pramipexole) .18 mg
Valium

Medical History - 10 + years past had significant problem of vomiting and weight loss due to an undiagnosed ulcer.

Experiencing (I believe) trapped gas resulting in abdominal pain and SEVERE back discomfort.

Can occur at anytime...but appears more problematic after eating a large meal.

Pain relief comes after a bowel movement and vomiting until all food has been emptied from my stomach ...followed by several loud belches.

Any help would be very appreciated.