its not sprained so whats wrong with it

my (right) foot is swollen 2x its orginal size, so is the rest of my leg up to my knee. went to the doctor she treated it as a sprain…then I went back and she just shrugged her shoulders. now I have a red rash by my ankle on the inside. and I have marks that look like scars from a scratch but there was never a scratch there and they are filled with fluid. I have pain from my toes to about half way up my (right) leg. its swollen so bad I can barely bend my toes. any ideas?