What Do Spreading Rashes On Body Despite Taking Prednisone Suggest?

I was diagnosed with poison ivy and tomorrow will be my last day of oral prednisone 4mg, six day course. I have also been using calamine lotion. However I am not better. In fact, some new welts and also small bruises have been appearing on my arms even today. The strange thing is that if there was exposure to poison icy, it was over two weeks ago. Why am I still breaking out, and when can I expect to get better? I m wondering whether I should even bother going back to the doctor, since all contact dermatitis gets the same TX. I m confused about the bruises though.