My boyfriend has been having pain on left side of stomach, burping and little appetite for the last week. is it his gall bladder?

Probably Not: Typically gallbladder pain is in the right upper quadrant and follows consumption of fatty foods (within 1-2 hrs. After a fatty meal). The pain can radiate to the back and can be accompanied by nausea and vomiting. Left upper abdominal pain may be an ulcer, gastritis, gas pains from the colon or constipation. I would visit your primary doctor to evaluate the pain.

Left abd pain: The gall bladder is on the right side . The left abd. Is a common place for diverticulitis.