Severe top leg pain, can't walk, low grade fever. c-section and ligation 3 weeks ago.

Fever, c-section: You should see the doctor, if you have a severe pain, unable to walk and have a fever.

Femoral neuralgia: You should see the OB/GYN who did C- section. "can't walk" has wide range from more painful when walking to complete paralysis. Level of concern is similarly variable. The anterior thigh pain is often a femoral neuralgia once thought due to compression under anesthesia; this has since been shown to be unrelated to positioning. It is common even late in normal gestation and more likely in diabetes.