go check out the definition of confidence in the dictionary, do you think all this overthinking makes you seem sure of yourself?

just go corner her ass, tell her you think she is cute but there is no time to talk to her in class and you want to get to know her better (seriously fucking sprint after her if you have to), start chatting her up for a tad, if she has somewhere to go, don't stop her for too long, either walk with her (in the direction she has to go in) or tell her you have to go too, then pull out your phone and just say, what is your number?

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the more sure of yourself and what you want the better, the more you dance around what you want, act unsure, wishy washy, can't just get to what it is you are about, the worse off you will be

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GOOD LUCK