Sally is 27 years old and requests an emergency GP appointment due to a 4 day history of lower abdominal pain. She is on the combined hormonal contraceptive pill and denies any missed pills and is currently on her pill free interval. She has a longstanding sexual partner and admits to recent deep dyspareunia and slight 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?