My son is 4 and he still doesn't know how to read any words at all, except his own name. Should I be worried?

At 4 years of age, children are still picking up pre-reading skills such as pronouncing simple words, developing vocabulary and writing simple letters. Most children start to read around 6 years of age. That said, every child develops at his own pace and in most cases, there is nothing to worry about. http://www.m.webmd.com/a-to-z-guides/features/when-should-kids-learn-read-write-math

thanks