Suggest Treatment For Pain And Swelling In Legs?

I am 55 years old, very overweight, (have been all my life), insulin dependent diabetic, and Bipolar.
Over the past six months I have had severe swelling in my legs and feet. I have been taking 80mg of Lasix as prescribed by my doctor. My legs still haven't gone down and now my knees are hurting so bad that I can't take the Lasix because I can't walk enough to get back and forth to the restroom. I have been seeing my regular MD and he is great but I think I need to see a specialist. What type of specialist should I see?