Confidence => projects secure person
Attractive men => get their confidence from their looks
Perhaps you are being too nice? I see so many guys that bend over backwards to help a girl. If you're being nice just to get into her pants then you're doing it wrong. Being a girl, I know what guys really want when they're a bit too nice to me. Most girls in that situation would just play dumb, and take advantage of you. They will see you as a useful pet that can help them with their homework from time to time. I am very attracted to nice guys. But the ones I'm attracted to aren't pushovers, they treat pretty much everyone equally (not overtly paying me extra care), but they are polite and will do little favours if it's not in their way.
In short: Being too nice, which the problem of "nice guys", projects a very needy image.