Pelvic Inflammatory Disease (PID): This condition is a strong candidate due to the combination of lower abdominal pain and bilateral adnexal (CVA) tenderness, which are hallmark symptoms of PID. The lightheadedness could be secondary to pain or systemic infection.

Ovarian Cyst: Rupture or torsion of an ovarian cyst can cause severe lower abdominal pain and tenderness, potentially radiating to the adnexal areas. Lightheadedness could result from acute blood loss or pain.
Ectopic Pregnancy: Although less common, ectopic pregnancy should be considered, especially if there's a possibility of pregnancy. It presents with abdominal pain, adnexal tenderness, and can cause lightheadedness due to internal bleeding.
Appendicitis: While appendicitis typically presents with right lower quadrant pain, atypical presentations can occur, especially in females. The pain can sometimes be diffuse or lower abdominal, and adnexal tenderness might be noted on exam.

Ruptured Ectopic Pregnancy: This is a life-threatening condition that requires immediate intervention. The symptoms can be similar to those of a normal ectopic pregnancy but are typically more severe.
Ovarian Torsion: Another emergency, ovarian torsion can cause severe pain and tenderness. It's crucial to diagnose promptly to preserve ovarian function.
Septic Abortion: If the patient has undergone an abortion, either spontaneous or induced, there's a risk of septic abortion, which can present with abdominal pain, fever, and systemic signs of infection, including lightheadedness.

Endometriosis: While endometriosis can cause chronic pelvic pain, it's less likely to cause acute, severe symptoms like those described. However, it could be considered if other diagnoses are ruled out.
Mittelschmerz: This condition involves mid-cycle pain due to ovulation, which could potentially cause adnexal tenderness and lower abdominal pain. However, it's typically not severe enough to cause lightheadedness and is less likely given the duration of symptoms.