Hello and welcome to e health forum.
Your symptoms and history appear to be due to Gastric reflux, gastritis or due to musculoskeletal causes.
Musculoskeletal inflammatory pain can be diagnosed if the pain increases on specific movements or on direct pressure on the affected area. Such cases of mild pain, subside on its own with rest. If needed anti inflammatory medications like aspirin or Ibuprofen 400 mg can be taken upto three times a day, to relieve the pain.
Gastritis occurs when the lining of the stomach becomes inflamed or swollen.
Gastritis pain occurs in the left upper portion of the abdomen and in the back. The pain seems to travel from the belly to the back. Other symptoms of gastritis include - Belching, Nausea and vomiting, Bloating, Feeling of fullness or burning in the upper part of the belly.
Treatment of your symptoms due to acid reflux or gastritis can be tried with over the counter antacids like Gelusil, tums, mylanta and acid reducing medications like omeprazole.
If they do not help, then, stronger medications that protect the stomach's lining or lessen acid production in the stomach are available by prescription.
You should consult with a gastroenterologist, who if needed can order gastric emptying tests, or endoscopies to diagnose conditions like peptic ulcer disease or gastric reflux.
You may consult your doctor for proper advice and appropriate treatment.