How long will the moon face go away?

I have been taking prednisone for about 3 weeks. I think I have a moon face. My face is all puffy. And I was just wondering how long will it take will it take for my face to go back to normal if I stoped taking prednisone now. And what do I have to do to get my face back to normal again. This is the second time I had the moon face. Two years ago I had steven johnson syndrom and I had to take prednisone for the pain. I had another episode about 3 weeks ago, and I had to miss a couple of weeks of school, I had to take the prednisone for the pain. Will it go away in a week or so? Can you just tell me how long it will go away. As soon as possible!