Guys, what's causing you to suddenly react to your crush messages slowly?

There is this guy that i met through mutual friends. He admitted that he is having a crush on me. Lately these past few days he became slow to reply and give excuses like he always had some other things to do. This happened after we had a serious conversation so maybe he wasn’t happy with my answer (not sure though). He used to reply right away but these days i feel he is withdrawn slowly from me and keep sending & posting sad quotes. What cause him to suddenly change this way?
Ps: he is a loyal guy and i do wanna win him back.
Guys, what's causing you to suddenly react to your crush messages slowly?
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