Why is he kinda avoiding me?

OK so yesterday a guy i really like and I kissed in the hallway. It was amazing and it made me smile! It made him happy too. later that night I texted him hey and I got a response from him every like 30 minutes and there were dud one word replies. Then he stopped in the middle of the convo! Then today he texted me first but he stopped again! Its frustrating cuz he treats me so good and flirts alot at school! I think he really likes me but- Whats his deal?