Funny you should mention this Devida. When I first started seeing a "gender identity therapist" this was central in my discussion. I wanted her to explain to me "why" . . . why should I want to dress like a girl when I am guy. She would never give me a direct reason (a few floating hypotheses) because there is no agreement in the literature or for that matter a true body of literature on what makes people crossdress. She did ask me why I was so fixated on finding out why and was it because I was hoping that by identifying the root cause I could somehow fix it. It was at that moment that I realized my inability to move forward and accept me (including Isha) was due to my incessant drive to find out why. So I gave up trying to explain it and accepted it. At that point I found true peace and was able to continue in my journey.
Hugs
Isha