What would be the reason(s) for a guy who's avoiding me after being really close (kissing, making out...)

I can't see what I did wrong. He had a crush on me, he always wanted to be with me he was even a bit clingy. Finally we made out one night and suddenly he has been distant overnight and avoids me now.

First I thought he was "playing" but after 3 months I'm not sure...I havent done anytging wrong i think, i havent changed my behaviour and i cant see what i can reproach myself...Why would a guy do that?