Back when I was on immune suppressants with the pred. I had the same effect & lost weight on them, even though I was on 60 mg of pred. I did not have the swelling in the legs that you have though. Maybe they need to do labs for your liver & kidneys, as I know those drugs can effect the function of them & cause swelling. I did have liver function trouble, when I got up to high on the methotrexate & immuran I was on, so they backed me down on my dose & my liver level did better, I had no energy when that happened, very weak. He is probably sending you to your pcp, do do all the lab work on you. They used to do labs on me every other week to monitor liver function, while I was on them.
Hope you get some answers soon!
Take Care Erin,
Mary