Since your pelvic inflammatory disease (PID) has persisted for three months, it is crucial to consult a gynaecologist immediately for a thorough re-evaluation, as you may need different antibiotics or further testing. PID is typically treated with a combination of broad-spectrum antibiotics to target various bacteria. Standard regimens often include a single injection of ceftriaxone combined with oral doxycycline and metronidazole for 14 days. For persistent cases, intravenous (IV) antibiotics in a hospital setting may be required. Please do not self-medicate; a doctor must prescribe the exact dosage and duration based on your specific case. Ensure your partner is also treated to prevent reinfection.