Can pain in teeth by applying forces of braces resulting in stress cause stomach problems like stress ulcer or gastritis?pain causes mental stress too

Emotional stress: Your collection of symptoms point towards the last concern. Mental stress. I believe you should discuss your concerns with a primary care doctor.

Pain/stress: Oral pain can cause diet and masticatory changes that can upset stomach. OTC analgesics can also cause gastric upset, as can stress/anxiety. A qualified Orthodontist can help you safely manage braces discomfort. Your General Physician can evaluate for GI dyscrasia, possibly referring to Gastroenterologist. Please seek care/comfort from all available practitioners.