He hasnt contacted me after sex! Why?

Its been about a week since we had sex. We're just friends (and ex's) so it was kinda casual. But before he texted me every day. Anyway.. I thought maybe he was waiting for me to text him, so i did. And he cut my conversation kinda short when he said he wanted to sleep. Im not being clingy for his attention or anything.. I just donno if this is normal for men. Was he pretending to be my friend just for this? Or is he just shy?