There are girls who would not hesitate to ask a guy out, and girls who would rather roll naked on hot coals than even think about walking up to an attractive guy.
Everyone's different, so don't assume that because they don't directly ask you out, they don't think you're attractive, and don't want to date you. You might be surprised how many secret admirers you have! I know my bf has no idea of how attractive he is, and that when people talk about him, they call him hot. The same could be true for you.
So like Vegged said, just GO FOR IT!!!
What have you got to lose?
http://www.healthboards.com/ubb/heart.gif *starry eyes*
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Life is a tale told by an idiot, full of sound and fury, signifying nothing.