Ohh, I felt very similar to how you do
I was deathly afraid of turning into "one of those" transsexuals... the ones who seem like they have lost their minds and everyone snickers at behind their backs.
So, I thought really hard about how to avoid that. Why it happened... and what I could do to make sure it didn't happen to me.
Basically, it is simply just being aware of how you really look and what actually works on you (and what doesn't). If you don't pass and just stick with androgynous clothes... you have no problems. But, if you don't pass and try dressing in little bright pink dresses with a stuffed bear under your arm... well... you might have to deal with more problems.
Really, long term... there is a LOT you can do to try and pass. Start off with hormones... try growing out the hair... trim some eyebrows... and just go slowly and see how things go. If that isn't enough, you can always try facial surgeries... or wearing corset to change the body... or even taking out a rib and implants to reshape your body! If you REALLY REALLY need to pass, you could probably get there some day with enough work.
But, more importantly (at least for me) was getting to a point where I was just comfortable. Living in a place that is more understanding and having friends / family who support you are a good step in that.
And, of course, DON'T focus only on transitioning and having "passing as a girl" be your main focus in life. If you do that, you will obsess over it... and drive yourself crazy. Get a career, work on the MANY other aspects of life besides if people think you are male or female. Even if people see you as a male, there is no reason you can't be accepted as "one of the girls" and have the same type of "girlfriends" experience and all that.
From the outside... if you read forums and other stuff written by trans people ... it is easy to fall into thinking that gender is everything about life. Many trans people seem to try to blame all their problems on being trans... and think that the answer to fixing everything wrong in their life is simply "being a girl". It is easy to start to think that the world is a cruel binary world where men run around fighting eachother and women sit around shopping... and anyone else is murdered. In my experience, this is SOOOO untrue. Sure, you need to be on the lookout for problems... and maybe if you run into issues, you should consider moving somewhere more accepting... but once you get to a place that doesn't have a problem, you will find life is pretty normal... and you can just focus on being happy

Don't give up before you have even tried.

There are TONS of people out there who will accept you COMPLETELY as trans... who really have no problems with it as long as you aren't running around in tiny pink dresses or anything else that is simply odd. Don't let being trans take over your life... don't rub it in peoples faces or be super sensitive about it (a great way to alienate others

) ... and you will be fine.