Thanks for posting on healthcare magic
John it just takes some men longer for their facial and body hair to fill out, but it eventually does for most people. Although some males are just more hairier then others and the amount of hair you have is not an absolute indicator of testosterone
levels.The basic cause is genetics in most of the cases . You can look at the men folk on your maternal and paternal sides of the family to get an idea of what your genetic traits are, as they relate to hair, you inherit these genes predominately from your mothers side.
Although if you are very concerned about your testosterone levels you can visit any doctor and get S. testosterone levels tested by a simple blood test
.If the levels are abnormal or low ,which is very unlikely , do visit an endocrinologist
for the further management.
But once your beard/mustache fills in and you have to shave every day, you may wish it was back how it is now!