My left leg has been hurting me for about 3 1/2 weeks now, swelling from angle to thigh, my doctor did an ultrasound about 2 weeks ago and the report was negative, gave me some meds for inflammation however it has gotten worse. it was in my calf area then moved to behind my knee, I work during the day and my leg would be swollen by the time I got home, I would elevate it at night but it never seemed to go down all the way, two days ago I couldn t hardly walk on it, after staying off of the leg for 2 days now the swelling has gone down but now the pain has moved to just above the back my knee to my lower thigh on the inside should I get another ultra sound & how soon, could this be a blood clot. I have Lymphoma and have had one before.