Can I sue??

Hello,

It is me Believer,and I am really upset. My father is in the hospital and suffering because his Dr. said, "it is cancer, you'll have wierd pains." Well my father has complained about pain in his leg, and actually was bed ridden because of swelling of his leg and foot. His Dr. for three months only once, after my suggestion, I am a teacher, not a Dr. checked to see if he had a blood clot. Well, to make a long story short, because of insurance, we had to switch DR.'s, Thank God! He saw my father for 5 sec.brought in his partners and they all agreed, he needed to go to the hospital now!! He had major circulation problems. He was told they would probably have to amputate his leg. Thank god they did surgery to prevent this for now. He is in so much pain, I will have nightmares remembering his face. My question is, was our previous doctor, negligant for not responding to my father's pleeds and concern earlier. Everyone involved cannot believe it has gotten this far.
thanks,
sherri