What Causes Severe Groin Pain?

hello my name is jocelyn, ive been having serve groin pain radiating down my right leg causing my knee to swell up. i was also having low grade fevers. ive went to the doctors 3 times and the emergency room and all they found was that my lymph notes were a little swollen. Other then that they cant find whats wrong with me, I can barely walk, sit up or even sit down. i lost my appetite completely. the pain is getting worse and i cant take it anymore.