No problem you are definetly not the first one to have trouble with this.
I think you are complicating things a little with the whole heart vs. head thing. Love is a little bit of both, otherwise you can end up making some pretty silly decision. The two have got to work together. There are other factors that are inhibiting you, too, like the fact that you think all GLBT's must be hidden because you haven't seen any, thinking they look a certain way, etc.
A lesbian/gay is just another person. They don't necessarily look any different, talk any different, act any different. Some do, some don't. But there is no universal gay look. W/ that said, just because you don't know a single gay person doesn't mean they aren't out there. What about those like yourself, who aren't sure? Or people who haven't come out yet?
So: simplify things. You feel attracted to both gals and guys, but more to gals lately. The thing to keep in mind (and we say this a lot) is that sexuality is fluid, meaning not all people fall on totally homosexual or totally heterosexual. You could be anywhere on that spectrum. So, don't necessarily worry about where you fall just yet.
I know you want to be in a relationship. But building one, or finding the right one takes time, and the faster you jump into them, the more problems you're going to encounter. So no matter whether you are with a guy or a girl, you need to go slow.
If you are looking to meet others, a good place to start would be GLBT groups. I did a little research, and found one that may be of interest:
http://portugalgay.pt/lang_uk.asp I have this one on the English version, but you can change it if need be
I think your resources are limited because the gay rights and recognitions movements only started in Portugal in the early 1990's, with the first group being established in 1992. But the movement's grown quickly, so I hope that helps!
Help yourself by helping the world
It's a pretty good day, I'm looking for tomorrow; I had a pretty good day, yeah, I had a good day