What can I do about having a crush?

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I've asked this question a billion times before but I'm really desperate. I can't tell any of my friends or family members since they wouldn't understand. So I'm here asking strangers for advice. The problem is I have a crush on an older guy (he's 20 and I'm 13). He is my friend and he treats me like his younger sister (he has a 19 year old girlfriend so he isn't a freak). I can't stand my peers because they are really immature so I hangout with older people. I realize we can't be more than friends since I'm barely a teenager myself and he's an adult but I can't help it. I really find him attractive and feel weird about it. I look at his Facebook profile everyday. I feel extremely nervous around him because of my feelings for him. I'm ashamed of my feelings. I'm really hopeless. Any advice?
No stupid answers, please.