Yeah, same thing for me, six months in... sigh.

I talked about it a bit with my therapist a week or two ago -- he says it's pretty normal, and most likely has to do with the growth "down there."
"This is one reason we warn everyone that that their sexuality will change," said he. He's a trans guy himself, so that's another reason I tend to trust what he says about this stuff. He says taking 45 minutes to an hour to get off is pretty normal; not for me, it hasn't been -- I've always done well to last 5 - 10 minutes.
It hardly seems fair that the sex drive skyrockets, and then THIS happens.