I think he's aware that you give him too much attention. I've been through a similar situation and i made a fool of myself by daydreaming that the guy acted like this because he liked me. Well, he didnt. And as soon as he noticed me staring at him/checking him out casually, he became more and more ignorant. This guy might be sweet and nice for other girls, but if he isnt the same for you too then he is not going to change that. U have told that u have tried to make conservation with him before which didnt work. My suggestion would be to just forget about this guy.