Can emotional/mental stress for a short period ( say 7 -10 days) activate h pylori in the body to start causing an ulcer which was otherwise lying dormant/asymptomatic or stress would only worsen existing h pylori damage/symptoms and is not the cause?

Ulcers and stress: Stress was once thought to be the main cause of ulcers, but it's now known that stress has nothing to do with ulcers. Helicobacter pylori is a common cause -- but stress has no known effect on H. pylori. If you have ulcers or have been diagnosed with H. pylori, discuss treatment with your doctor. Of course deal with stress as best you can, but it won't make any difference in an ulcer problem.