Start with a primary care doctor who then, if warranted, can refer you to a gastrointenstinal specialist.
That you mention anxiety and stress,
that does align to one of the things
that goes hand in hand with irritable bowel syndrome. It's important to note that IBS is different for different people. And can change back and forth in the same person as well. If you have anxiety, it may be beneficial to see a therapist for this and begin working on that. Overall, that could help your life.