I Was Sunburned 3 Weeks Ago In LA. Then A

I was sunburned 3 weeks ago in LA. Then a week later I went swimming for about 40 minutes and had on SPF 30 and reburned
For the past week my burn areas- both upper arms and shoulders are ITCHING like mad. I went to urgent care last Monday and was diagnosed with sun poisoning. Got steroid injection, a medrol pack and 3 tubes of an anti itch cream. It seems to be getting worse I'm laying in bed right now not able to sleep because my arms it h so bad they almost hurt
Help