Thanks for the additional information.
There are so very many things that it can be, that you need to see someone in person. Here are the possibilities:
Upper quadrant: reflux, liver, gallbladder, pancreas, lung, heart, muculoskeletal.
Lower quadrant: Bowel (diverticulitis, ulcerative colitis, irritable bowel syndrome, Crohns disease, appendicitis), reproductive (endometriosis, tubal pregnancy, infection, ovarian cyst), etc.
Reflux can be treated readily with medication and lifestyle changes (raised head of the bed, no food 3 hours before bedtime, and avoiding triggers like alcohol, chocolate, soda, fried foods, acidic foods, coffee, etc.), weight loss if overweight, etc.
Please let me know if you have additional questions about this.