Allergic reaction to penicillin

I had an allergic reaction to penicillin Tuesday.  I had been on Amoxicillin since last Thursday with no known side effects.  On Tuesday morning my  lip started to sting and swell. I suspected that something must have stung my lip until a co-worker told me it looked like I might be getting a fever blister.   Around four-thirty I while driving home I decided to stop at one of the local walk-in-clinics to see if they would give me a prescription for fever blister relief.  By the time the doctor was able to see me I had a rash from my scalp to my waist.  After talking to me and looking me over he told me I was having an allergic reaction to the amoxicillin and that  I am now allergic to penicillin.  He had a nurse give me two shots one in the arm and the other in the hip.  He said the shots would help relieve the symptoms and stop me from going into shock.  He also gave me a prescription for hydroxyzine.  I had to stay at the clinic for twenty minutes after the shots in case I had any side effects.  I started to shake uncontrollable and became cold.  They said that was normal and sent me home.  I hated to drive while shaking so bad but made the mistake of doing it anyway.  I also stopped at the local pharmacy to pick up my prescription.  I was shaking so bad that I could hardly sign my name and people were looking at me as if I was a drug addict  coming off drugs.
When I arrived home I went to bed and was asleep by ten  o'clock.