If this rash started up fairly quickly and spread fairly rapidly, it's unlikely to be skin cancer. Could be a fungal infection (
tinea versicolor), or any number of other possibilities. What you ought to do is go to Google and search "Images" for "white spots on skin." See if any of the photos match what you have on your own body.
This is
tinea versicolor:
http://tinyurl.com/cacegb Ever since ESRD screwed up my immune system, I get fungal infections on my skin every time I take antibiotics.