What Causes Abdominal Pain After Food Intake?

I have been experiencing pain in my left abdomen after I eat for 2 days in a row. I also have this continuous pain below my left shoulder blade for months but only at night when I sleep. I have a gallstone which showed up in the ultrasound two years ago. I went to see the specialist about this but because I did not exhibit any gallbladder stone symtoms and the stone was a the bottom of the sac so the specialist told me surgery is not needed. I do also have a tiny bit of pain in the lower back the day two days ago. The pain is tolerable so I have not take any medications. Please diagnose my problem..thank you..sue