How To Get Rid Of Blistery Rash?

Since November I have been fighting a rash, and in Dec. my lymph nodes were swollen and I also use the bathroom to a lot more than usual as far as diarrhea, it's more solid but loose since I eat. My doctors keep treating me for a dermatitis but it does not go away with prednisone and creams. it's a blistery rash that seeps.