Can/should I sue if I went to an urgent care center and they failed to find blood clots in my thigh, calf and lung?

In mid-May, 2012, after a considerable amount of time (weeks) feeling ill and in pain, I went to an urgent care center. I told them that I had a fever, chest congestion, and pain in my left leg. I also informed both the receptionist and treating physician that I knew it was not a cold or flu and if it were either, I would have treated it at home. I was prescribed pharmacy cold medicine and antibiotics. Three weeks later when the pain in my leg became unbearable, I went to the ER where an ultrasound found clots in my thigh and calf. A whole body scan found one in my lung. I was hospitalized for 6 days. This could have easily been a fatal misdiagnosis. Could/should I pursue legal action against the urgent care center?