PredniSONE and black spots

I was on Prednisone for just over two weeks for a bad skin rash (allergic reaction). I went to the ER they gave me an injection on Prednisone. The next day my Doctor puts me on 40mg a day for 10 days then down to 20mg, and then 10mg. The side effects were (and are) crazy. Blood sugar and Blood pressure are through the roof. My heart pounds,races, skips beats. Hands shaking, nervous, and panic attacks. Yeah, sure, the rash is gone, but I feel like a train wreck. I took my last dose 2 days ago, and have been told it can take 2 to 4 weeks for this to get completely out of my system and end the side effects. Can anybody else verify this?? Good god, what a mess!!