Why is he acting this way suddenly?

Hello, so I am not an expert but here is my view: This has happened to me and it's usually because they do/did like you. He probably was checking you out to see if you were his type and giving it a chance. Now, he might be trying to get it accross that he wants to be friends and no more or maybe that you talking to him is annoying. Often times us females can be rather clingy when we like someone without even realizing it so he might be trying to push you away in the only way he knows how. My advice: just don't talk to him anymore. If you want him to like you then distance yourself a bit. guys like the chase. :) hope i helped