Another trans INTP to add to the mix. I will agree with the original poster about feeling different for my entire life, but I was born physically male and have been transitioning for nearly two years, but it's been slow. Also, I will agree with feeling kind of in between. Female pronouns, please.
It's definitely something that has to be thought out and a psychiatrist helps. He or she may even be nice enough to give you a prescription depending on where you are located. I got a prescription the first time I saw my shrink and was incredibly appreciative of it, but that was pretty much after hiding away for five years like Lauelin did. Also be aware of not having to pick a side per se. You can be androgynous like I am right now or genderfluid or something else; you don't have to pick male or female if you don't want to. Pick what makes you the most comfortable, which is what this whole thing is about, what makes us the most comfortable.
For instance, I started transitioning in my mid twenties but I went into the shrink's office for the psychological effects of the medication rather than the physical effects because I thought I would have a difficult time passing if I decided to fully transition, which I have chosen, by the way. Being six foot six, quite muscularly toned at the time, and what many people thought of as a very handsome man (that makes me want to vomit just typing it), I figured that I was essentially fucked. That was not the case, though. I'm actually pretty androgynous at the moment, which is something I see as an improvement, but physical transitions for MtFs can take upwards of three years not including full breast development which can take as long as ten. So, in general, I present androgynously, and sometimes I flip-flop with some fluidity for work for example when I have to be out for a work contract or something. I'll end up putting on a suit and pulling my hair into a topknot because being an engineer is still an old boys club and I'm in the position of currently being able to present as male if the need arises and dropping my voice seventy hertz back to its natural level helps, too. I'm really trying to keep everything androgynous at the moment until such time as my body catches up.
There should definitely be a weighing of the pros and cons when thinking about transitioning. Ultimately, it comes down to what you feel the most comfortable with, but the path is paved with many things unwanted. Firstly, hormones will result in some irreversible bodily changes. Secondly, you may be fired from your job depending on where you live. Thirdly, you will probably end up losing some of your friends and family. My family disowned me and I haven't talked to them in over a year, but the trade off is I am no longer suicidal from gender dysphoria, I feel more comfortable with myself, and I'm happier. And running from it seldom works. I tried to do all the manly things like going to the gym and bulking up, which was stupid in retrospect, drinking excessive amounts of beer in the name of male camaraderie, going out with the guys, et cetera. But that was all just an act. I always fit in better with females ever since I was very young and women seem to more accepting of transgender people, in my experience.
It's a lot easier to make decisions such as this when one doesn't give a damn as to what other people think. I know I don't and people don't fuck with me for some reason. Maybe it's my height or my dead eyes, or the fact that people tell me I'm intimidating, which I never really understood, but I'm happier overall than I was before.
Feel free to ask me any questions.