What else can i do for a drug allergy?

I didn't know it until yesterday that i am allergic to penicillin. Well i went to the doctor because i broke out in rash all over my body and he gave me a steroid to handle the inflammation. They also told me to drink a lot. Today i drank 2 glasses of tea and 3 glasses of sunny D. went i went to urinate a few minutes ago it stung a little. what could that be from? also i took some allergy medicine to help the rash not itch as much. I would just like to know what i can do i feel horrible!! thanks for any answers!