I’m into him so…

Try telling him

If that’s the case, it is better to confess and know what he thinks about you. And then act accordingly.

Wouldn’t it ruin my chances of getting closer to him?

Do you still want a guy who flirts with and makes you feel things but next moment talk about his crush?!
There are also possibilities that he isn’t really crushing on any else but you. May be, he just want to know your reaction. So, don’t ask him directly. Make some obvious hints and let him know about how you feel. If he feels the same, he will confess it. If he says no, then it is better you move on! He is just keeping you to kill his time.