CodeVeronica, I don't think you are overthinking it and it is reasonable to reflect on your own motivation and the morality of it. I can say that while I had a somewhat looser moral framework growing up, I still face the same questions after many years of CDing.
I also admit that my reason for CDing is largely for sexual gratification, and I also am not attracted to men, similar to you. So, for people who feel this way, isn't the act of crossdressing really similar to an extended form of sexual self indulgence? What is your moral position on that?
For me, if I tear down the pink fog for a little while and think clearly about things, I feel that it is fundamentally morally wrong. Sorry to say that, but it is true (for me). It is of course easier to avoid the guilt and try to rationalize why this form of behavior is acceptable in the name of self-expression, etc.
So you may also ask the question of "if it is morally wrong, what am I going to do about it?". For me, I have arrived at the understanding that this is a flaw in myself that I cannot erase, so I will continue but I will hide it away and minimize the impact on family and friends.