What the hell is with him?

no it doesn't make you shallow. i believe you cant date someone that you don't find physically attractive. anyway if he has changed then its not up to you to change yourself to get him to like you. You should just be yourself. although saying that if he looks at you don't look back at him, pretend you don't even notice him. if he talks to you in a nasty way like the 'buzz kill' comment then just look at him like he is an Absolute idiot and child for saying that. If you are abit more y come back with a comment about how he looks or what he's saying or if you cant be creative just say wow your so not a child or aren't you suppose to be in sixth form, grow up something simple. Boys can normally tell when a girl likes them purely because girls are so obvious. anyway he'll then think your completely over him and start to get jealous. you may then notice a change in him, talks to you/smiles at you etc But give it time don't expect to have him chasing after you in a week :) Hope this helps!