A 24 year old lady presents with a 5 day history of lower abdominal pain. She is currently on the combined hormonal contraceptive pill and denies any missed pills. She has a longstanding sexual partner but does report recent deep dyspareunia and slightly thin vaginal discharge last week.
On examination she has a fever of 38.2 °C with otherwise normal observations and mild lower abdominal tenderness. On internal examination, you observe adnexal tenderness and the cervix looks normal.
What is the most likely diagnosis?