Scaredkiwi.
I suggest you do whatever makes you feel comfortable with yourself.
You can annalyse yourself and your past till the cows come home, to try to explain every aspect of you. But to what end?
If the rape is bothering you, that is, if it is occupying your thoughts to a point where you are uncomfortable then you should try to get some support. From whom is another matter. That is really up to you and how you feel.
I'm not trying to diminish the terrible offense against the body and the psyche of any sexual assault. But at the same time, I've found some people seem to try to make more of it than may be appropriate.
Your question is, is the rape the reason why you are transgender and gay?
That leads you to the next question, if you get successful support for this incident, will you stop being transgendered and gay? Do you want to?
On the other hand, if you don't, will you be disappointed? Will you feel support is unsuccessful if you continue to be transgender and gay? Will you resist support for fear of no longer being transgender and gay?
What I'm trying to say is, you are tying one with the other. which suggest you are looking for reasons for being transgender and gay, rather than seeking support for the rape.
Rape is a particularly incidious offense, especially against young children.
But we will each end up beating ourselves up if we seek to link something in our present which is causing us problems with things in our past.
In a way, it's a bit like the old thing with many in their teens and twenties where they blame their mothers for their current problems.
hope this is of some help.