I had sex with a close friend and now he’s ignoring me?

I have known this guy many years. We have always had an intensely close relationship, nothing has ever happened between us over the 15+ years knowing each other as we have both crossed paths with other people in our life. We always swore we would value the friendship over anything sexual, but two weeks ago out of the blue we ended up having sex. I was drunk, he was sober, it was amazing, and afterwards we both agreed it had been a long time coming. After he seemed upset, he said he was worried I wouldn’t want to be friends anymore but I reassured him I would and that it doesn’t change any tbh itv between us. He said he didn’t regret it but felt bad for me as he always swore he wouldn’t do this to me ( I assume he meant use me for sex) he then quickly dropped me home but was loving etc, the next day he messaged and we spoke as usual; he asked to meet for lunch like he usually does. The rest of that week he didn’t message, I did a lot and got a lot of blunt replies if any. I guessed I must have somehow hurt his feelings so a week on I apologised, he said he was sorry too and he had just had a busy week. I then messaged 3 times over the weekend which he has left me on read on all 3 occasions. I have decided to leave him be now, but I feel hurt. Why has he done this? We had spoke of sex a lot over the years but he always said if it ever did happen he wouldn’t just throw me away afterwards.

Updates
11 mo
Forgot to say it’s been 3 weeks since and he’s only texted once, which was a far cry from the usual everyday text I received before.
I had sex with a close friend and now he’s ignoring me?
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