How can you relax your stomach when it tightens from stress and anxiety ?

Many ways: You can practice various forms of relaxation exercises, including meditation, visualizing a calm place such as a beach, or actually tightening your stomach further, then relaxing it. If your stress and anxiety are disrupting your life, counseling and/or medication can help. Seeking a mental health evaluation could be of benefit if your stress is very burdensome. Hope this answer helped.

Abdominal breathing: Deep breathing, or "abdominal breathing" can be a useful technique for relaxing abdominal muscles when managing anxiety. Progressive muscle relaxation (pmr) is another useful technique. Information is readily available online, with cds purchaseable from retailers that guide through the process.

ANXIETY: 1st have a physical exam by a Dr. to determine if you have a physical illness. If you are cleared consult with a Clinical Psychologist for psychotherapy to help you with ZOOM & a Psychiatrist for medication. Your fears and anxiety could be heightened because of the Covid-19 pandemic. Stay safe, cautious & hold on to hopefulness to elevate your immune system.