Take care WD40 and get well soon. If/when you next have a blood test, ask them to check your vitamin D levels. Many people are vitamin D deficient (there is some debate about the definition of 'deficiency'). This can be the case even in a sunny place like Singapore, where a lot of people spend most of their time indoors.
http://www.vitamindwiki.com/Shingles+and+vitamin+D