Why does he shake around me?

Ok so I have had this crush on this guy for a while, and he just found out like a month ago, and he hated me last year and now we are friends. When I talked to him, I feel awkward. But this morning he came to school with purple duct tape and he was making me and my friends duct tape bracelets and he measured my hand with the duct tape and my friend Tess was there and she was like to my crush, "Why are you shaking?" and he was like "Shut up." What does it mean? Why was he shaking? Plz noooooo rude comments thanx :X