I don't think that not knowing *why* one enjoys something is a problem. Do we know why anyone enjoys anything? Why do some people enjoy licorice and some people hate it? Why do some people enjoy heavy metal and some people hate it? No one has an internal conflict about why they hate wearing suits while some other people love wearing suits.
The difference is society says that crossdressing is *weird*, or *wrong*. Because we feel that it's something we shouldn't do, we look for the reason that we enjoy it so that we may eliminate the cause and be "normal".
So, ask yourself: "Is my crossdressing *wrong*?"
No? Good! If it's not wrong then why should we worry about why we have this desire? Just let it be any other part of your personality, like any of your other passions in life!