Is he using me for his own sake? what should I do?

well me and this guy josh have been talking for a couple months. we've known each other since 6th grade and we've always been best friends. . .until now. we've been getting closer and closer. but now i'm thinking that he just used me. he gained my trust and made me believe he wasn't like all the other guys and what not so I trusted him and actually started to believe he felt the same way too. So one night, i slept over his house, and we hooked up, which i've never done before aside from my recent ex of 3 years (just so you don't get the wrong impression of me) and that was last week, and since then, it feels like he's not even trying anymore. When i talk to him, i get one word answers and I feel like i have to carry the conversation. So i'm thinking, why should I give a damn if he clearly doesn't?