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I (27F) have had sex with this guy (25M) twice so far.

The first time the chemistry was extremely strong. We had sex for hours and it was one of the best I had and I could tell he was very into it aswell. When I told him I was engaged (I’m in an open relationship), he got visibly startled. After that we went our separate ways. We didn’t have a lot of online contact.
After a month or so I saw him again, ignored him on purpose, and he got irritated. I then deleted him and he blocked me.
Recently we ran into each other again. The physical chemistry was immediately intense again. We had sex (shorter this time) and he came inside me, even though I told him I could get pregnant right now. He reciprocated everything I said. I said I thought about him often and I wanted him many times, and he said me too, you don’t even wanna know. That night/morning it ended pretty awkwardly because he was tired after his long shift.
After that I initiated contact online. He replied, but it was short and low-effort. I then suggested meeting again soon, he went completely silent. It’s now been over a day and a half with no reply.
He knows I’m engaged and in an open relationship.
My question:
What does this combination usually mean?
Can someone be genuinely very attracted and still go silent like this after a clear invitation to meet again?
Is this more avoidant behavior, low interest, playing games, or something else?
I’m only looking for good sex and chemistry, not a relationship, but the inconsistency is confusing.
Any insights would be helpful.