You know, I was thinking of making a topic about this, seeing as I've been a bit sex-crazy ever since I embraced the fact that I am not male and started shaving my legs and doing things to try and feminize my body...
Before I did that, I was maybe able to "do stuff" once every day or so, but now, I'm pretty much jumping on all of my boy/girl friends round the clock like "hey, wanna screw me?" My thought is that what's been keeping my libido down all these years is a form of dysphoria, and feeling like I'm actually sexy on some level is making sex way more fun than when I used to go through the motions of pretending I was a pansexual cis-male. (well, aside from "being on the giving end" with a male) Fortunately, all of my partners have been pretty on board with this: I was open with them about the non-male thing from the beginning, so it's not a complete shock that I've transitioned in the bedroom. I'm just so much more comfortable about it all, and it's just so much more fun to be able to fully embrace it outside of my head.
TLDR: I think the sex thing is related to a lessening of unsexy dysphoria when you're doing effeminate things.