Guy's Behavior

Why did he block me after sex?

There's this guy I knew since elementary. I would say our friendships and close relationships were on and off and would last a week or a couple days. Like we could never stay in touch for about 2 weeks. It's like a cycle, on and off, we always come back to each other... well him. it's a weird situation with him. anyways two months ago we hung out and it was a night drive. Nothing much happened, we just kissed. next day, he wants to forget about it, I say okay and try to forget about it. then a couple days later I get blocked over the dumbest thing. but that's not the point. he eventually unblocked me apologizing, telling me he feels we have some sort of bond and asking for sex. the clown I am I say okay but we never hung out after that because he stops talking to me the next day. he sounded desperate in my view. last week I reached out to hang out. the following day we had sex. on my way home I receive a messaged from him about he feels like he sinned? I mean he's not religious, and it was our first time having sex together but not our first time having sex, so did he let me off easy? then he blocked me for literally no reason. I didn't know how to react because he blocked me before but deep down he made me feel worthless. i felt like crying but I couldn't. I don't know what to think of this guy.
Why did he block me after sex?
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