Hi and welcome to HCM.
There are many possible causes but most common are gastritis
, GERD, gallstones or IBD. When you rule these out then some more serious diagnosis should be considered. YOu should change your dieatry and lifestyle habbits and see will it improve. This is the best treatment. Also you should take some antiacid medicines. To check your liver,gallbladder
you shoulds do abdominal ultrasound
and then plan further tests. Wish you good health.