My feet and lower legs swell at times and sores/blisters filled with clear liquid appear?

I want to explain first that I am 5'10, 350lbs. In the past two years I have gained over 100lbs. I am on the medications Suboxone 8.2 mg 1 time a day but I also abuse my other medication which is Ritalin 20 mg. I take 7-9 a day but prescribed only 3. Off and on over the past year my feet swell and sometimes hurt. My lower legs swell also from about 5" below the knee down to my feet. My legs will break out in these sores, raised bumps that are usually filled with a clear liquid. The bumps/sores are not always all round. Some can be more like a 1/2 inch to inch long. Also, at times, usually evenings, my legs itch so bad its unbearable. What could be the diagnosis or cause? I have a doctors appt in a week. Any help is highly appreciated. Please excuse the bad spelling n grammar.