If you can get in to see a doctor, you should. It could be many different things. Could be gas, indigestion, acute pancreatitis, or a few other things. I'd skip the general practitioner and try to go straight to a GI. They will probably run blood tests at first. Hopefully that will help figure out the exact cause.
I'm not sure if it's acute pancreatitis. I looked up the symptoms and I don't have vomiting or fever which are apparently the main ones.
I am not sure if you have some Yeast overgrowth ...one easy treatment is to avoid all foods and breads with yeast, sugar and cheeses. Drink pure milk, pure juices and fresh fruits...no grapes or grape juice for a month at least.
to drink fill up a glass with ice and put in some water ..this is what you should drink at least 9 times a day.
If feeling better, it probably was the yeast infection ..will need at least 6 months of above dietary restrictions.