I said the answer on this is one only you can find. Someone might be able to say "Yes, I was the same, now me and my wife have biweekly Ménage à trois' with a Thai ladyboy" and it will click in your head "YES! Transexual Southeast Asian prostitutes, that's what's missing from this relationship!" but that is just taking pot shots in the dark and hoping you strike lucky, in the end you're going to have to find the answer within yourself.

You say nothing is missing, but unless you have an addiction (in which case seek professional help) something clearly isn't right.