Is he interested or not?

Hey, there is a guy in my class who claims that he's an introvert (and I guess, shy too) and a month or two ago we began texting each other. We both are 17. I had shared a secret with him after which he shared about a girl he liked. We got a little closer but I was irritated and stopped talking to him much. However, our convos were on. Some time later I regained interest in him. He initiates convos but doesn't talk much except for "sup" and all. He's flirted once or twice. He doesn't talk to me in person, i.e. in class. We meet almost daily in class but he doesn't approach me. He says he likes being quiet. On text, he has stopped talking about other girls and says the one he liked, was just casual liking. However, on chat, he talks lesser than he used to. Is he interested or not?