I also can have stomach issues when anxious. I agree that this is pretty common. A Tums might help at these moments. :>) One thing about vitamins, I have to take them at night as I can get a little nauseated from vitamins for some reason. I take mine before bed.
By the way, have you seen a doctor. Gastrointestinal issues ARE very common in general. Example, I was suffering GERD or heartburn. Drove me nuts and I never knew how GERD could become so bad that it kept you from doing things. I took an antacid for it. Found that when I changed some things around like limiting carbonated things/coffee/etc. and losing a few pounds--- it got better. But that antacid pill really was helpful when I was having it. That can feel almost like a heart attack. But know it is just GERD and treating it makes you not so much scared of it but annoyed by it.
So, see a doctor for any medical reasons you are having GI issues. Anxiety can play a role but it may also be something easily treated. And not anything serious. And then it would help with your anxiety about it to understand this. good luck
Are you on any new medications? This is a common symptom of anxiety, but it can also be due to other things, including medications and diet -- as we age, our digestive systems can change, and things we've been doing for years that weren't right for us catch up to us. Something else that does this is some multivitamins and iron supplements. Anything new?