Any updates? It is important that you get evaluated by a doctor. If no insurance, consider free clinics in the area.
This symptom checker from familydoctor.org can help narrow down possible causes:
However, you still need to see a doctor, sooner rather than later.
Accurate diagnosis will likely require labs and/or imaging tests.
For example, your doctor can check lipase to rule out pancreatitis.
Pancreatitis can, indeed, cause back pain: https://www.mayoclinic.org/diseases-conditions/pancreatitis/symptoms-causes/syc-20360227
Please return to your doctor sooner rather than later to discuss your new onset back pain.
Yes, you should see a gastroenterologist for further workout and management. You might have H. pylori infection, pancreatitis, or something else.