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Sudden and severe pelvic pain, often with nausea and vomiting, is often associated with inflammatory changes in ovarian cysts. They are more pronounced due to cysts rupturing and resulting in internal bleeding.
Since tests already have been done and they have ruled out ovarian torsion and other complications, it is likely, that your symptoms could be mainly due to inflammation.
Functional ovarian cysts usually don't need treatment. They usually disappear within 8 - 12 weeks without treatment.
Taking pain medications might help to a major extent. In case they are not helping, treatment with prescription medications like Naproxen or Ibuprofen might be helpful.