I Had A Sudden Pain On My Stomach At 9pm

I had a sudden pain on my stomach at 9pm so I drank milk and took tums but the pain didn't go away and stayed till the next morning. it only happens at night and feels like I have severe gas. Was in pain almost every night if I eat something at night. and I wouldn't have any pain if I skip dinner. got scheduled for an endoscopy after a month since this first started and the doctor said that everything is normal. I still have pain only at 9pm or 10pm. I recently started on Beano right before dinner then I don't have gas pain on my stomach. Any idea why I am having this gas pain all of a sudden? By the way, they told me that I have 10 mm gallstone earlier this year. am I having problems with gallbladder or pancreas?