Talk to Gastroenterologist on Intense Abdominal Pain

hey, It started 4 to 5 years back my father feels acute pain in abdomen specially in night biyearly ,we take him to emergency and doctor give him a pain killer injection (diclofenac sodium) and the pain is gone. But from 3-4 months this pain become intense and occurring frequently, like after every 2/3 days. we visited our doctor and after the ultrasound he said the problem was due to a swelling of gall bladder he gave the medicine and after two weeks of treatment there is no swelling but the pain becomes more severe. kindly recommend a doctor for the treatment. thank in advance