What Causes Persistent Pain In Abdomen Radiating To Back?

I ve had a mild pain in my upper left abdomen for over a year. Over the past 3 months, the pain has increased dramatically. I went to a gastroenterologist, had an endoscopy with mild gastritis, and a nodule on my esophagus. I was prescribed prilosec, which I ve been taking everyday since 10/17. Now the last 3 days I ve been experiencing unrelenting pain in the same area and it s moving towards my back as well. It now hurts to walk, sit, lay on my side and breathe. Is it possible that it could be gas? I called my dr but my call wasn t returned. Should I wait until my appointment next week it should I be seeking other treatment from someone other than a gastroenterologist?