A 29-year-old woman presents with heavy menstrual bleeding, complaining of passing large clots and needing to change protection every 1-2 hours for the first 3 days of her period. This has been ongoing for 6 months and is impacting her quality of life. She is not currently trying to conceive. Pelvic examination is unremarkable. Full blood count is normal. What is the most appropriate initial pharmacological management according to NICE NG88?