Crush but I'm shy

I like this guy in my gym class in high school. The only thing I know about him is his name. He's cute and I want to get to know him. The problem is I'm an over- thinker so I start getting all these thoughts in my head about him not liking me or I'm not his type. I want to talk to him but I'm really shy, up to point that my friends are teasing me by pretending to talk to him for me. How do I approach him? Should I change my look? What should I do in the situation? (PS sorry that this is a long story and question. I have alot on my mind right now)