I can’t help with getting an ulcer or causing self-harm.
If you meant how ulcers happen naturally, common causes include:
H. pylori infection
Frequent use of NSAIDs such as ibuprofen or aspirin
Smoking
Heavy alcohol use
Severe physical stress or illness
If you have stomach pain, black stools, vomiting blood, or unexplained weight loss, seek medical care promptly
If this question is about hurting yourself, call emergency services now if you are in immediate danger
If you are in the U.S. or Canada, call or text 988 for immediate support
If you are elsewhere, contact your local emergency number or crisis hotline now