I'm gay and I keep leading girls on?

I guess it isn't apparent that I'm gay, because 75% of the time girls I talk to end up liking me... A lot... and I don't reciprocate... and I end up feeling like a dick about it. I don't really want to be openly/outwardly gay. I wouldn't say I'm "closeted" either, because those who I feel should know, do know. I wouldn't want people to assume I'm gay for a multitude of reasons... Mainly, I'm in High School in a not-so-great area, and because I kind of advocate when I hear other kids bad mouthing gays. So, letting everyone know is an option, but the cons greatly outweigh the pros. Suggestions? kthx