My first symptom was gastrointestinal related. I went to the Gastro and had an endoscopy, CAT Scan, Gasto Sonogram and other testing done. I know exactly what you're doing through!
What helped me, initially, was Apple Cider Vinegar. Two teaspoons in a glass with water and some honey, chug it and my reflux went away for awhile. It'd only get bad if I ate really greasy food or drank a lot of alcohol.
I eventually realized it was anxiety when it flared up again when my grandmother and Mom both went into the hospital in the same weekend. I felt fine that weekend... Calm, cool, collected. Worried, of course, but not stressed and I didn't have any symptoms. Then that Monday at work it hit me. My Mom was home and my Grandma was doing OK. Like a freight train! BANG! It wasn't just my stomach; Rather, it was my whole body felt like it was on lock down. I felt like my chest was going to rip itself open it felt so tight. I had never felt such a way. It was the epitome is of discomfort. I left work and made it a few miles away and had to call an ambulance because I couldn't even sit up straight in my car. I'm 25... I shouldn't have to worry about such things, but anxiety generates these illusions and the physical manifestations come out.
Anyway, I still have some stomach issues. They come and go, especially when going onto new medicine (Which I believe is the extra Serotonin in the gut). But that goes away.
I suggest the Apple Cider Vinegar thing. It tastes terrible... But it's cheap (Google "Braggs Apple Cider Vinegar" [I think that's how it is spelled]) and it contains a bunch of micronutrients as well. Just don't take it straight. Bad idea. It's bad for the esophagus as well.
Otherwise, antacids help. Try Ginger Tea. If you have a hard time eating foods, try making a smoothy with everything you need vitamin-wise. I would sometimes make smoothies with Almond Milk, Chocolate Almond Milk, Protein Powder, Strawberries, Banana, Kale and so on. This way you can drink it at your pace and it's easier to go down. You don't have to sit there chewing, which caused nausea in some instances for me.
Lastly, Xanax helped me a TON, especially when getting used to new medicine. Many people say it has a high potential for abuse, but it has been a miracle pill. I try not to take too much, but for awhile my stomach was so bad I had to take one every morning just to get through work.
Best of luck to you!