Thyroid,autoimmune,celiac and vitamin def are normal but my hair is dry and thinning, skin is aging, pale, loose stools. can it be low stomach acid?

Anxiety: At age18 , traumatic experiences of childhood, unresolved emotional conflicts, stressors of relationships, work and finances can cause Anxiety. Anxiety can express by physical symptoms-dry hair ,changes in skin and loose stools. These symptoms are not due to low stomach acid You have good physical health as shown by normal lab tests See a Therapist to cope with stressors ,and to resolve conflicts

Perhaps but also:: Your symptoms could have many causes. "Normal" thyroid tests don't rule out thyroid issues- see http://tinyurl.com/koyamo5 Low stomach acid is possible but uncommon at your age: http://tinyurl.com/qb7zase You might be deficient in essential fatty acids, have gluten or other food sensitivities despite neg celiac test, have intestinal parasites (common & hard to diagnose) etc. See integrative Dr.