I have been having this pain since last June. The back of my knee is even swollen. My leg is slightly swollen than the right leg, just enough to notice. Had a D-Dimer test done in the end of June and it was negative for blood clots. I am a 22 year old female, not pregnant, and no birth control. Am I just overreacting?? Been to the doctor 4 times for this and chiropractor multiple times as well.