Your feelings are completely valid, listen to them
If the guy is kind and respectful, try to talk to him about how you are feeling, he might be good support. He is probably wondering what he did wrong!
I felt like this after sex at 16, all through my teens and into my adult life, through marriage as well. I was into the person but didn't enjoy sex, it just felt like... nothing. And I would be left with this sense of longing and emptiness which would have me repeat the experience to try to get the feeling of emptiness filled. Turned out I was gay 🤦.
Point being that I didn't listen to my feelings because I didn't know how to, or even that I was allowed to have feelings about anything but the norm.
So, listen to your feelings, and listen to your body, it will tell you what is right for you.
Maybe you just aren't attracted to him enough, maybe you aren't attracted to anyone, maybe you are suppressing who you are attracted to. It's all fine and you have the right to feel what you do and not feel socially pressured.
First time sex, even with a new partner can sometimes be clumsy, over very quickly (with men) and not be great.
But if you aren't feeling a desire to touch them in that way, it isn't attraction. You might like them, even love them, enjoy their company, love their face.....but sexual attraction is when you see a glimpse of skin or see them naked and you have an urge to touch them in that way. I am spelling that out because it was never spelled out to me what it was supposed to feel like, so I carried on doing what society expected.
Good luck, and keep listening!