I'm having bad pelvic pain. how can a little uterus lead to so much pain?

Exam: The uterus may be the source of the pain or there may be other causes for your difficulties. I'd suggest a complete gynecologic exam and possible medical imaging to help you find the source for your pain. If these are normal other causes of pelvic pain needd to be explored.

See Gyno: The uterus can be a major source of pain. See your gyno. I can't be much more help without more history.