How do I navigate my first ever crush / fantasy?

I'm 21 and have never had a crush growing up. I've had people I've been really attracted to, but never had anyone that's strongly occupied my mind until now.

There's a guy that I've been watching online who for a while I really admired I saw that he was attending a community event that was near me so I wanted to help out and attend. I had a great time talking to people and helping out.

During break he came to our table to introduce himself and we started talking for ages. He was really charismatic and interesting. Once we left and I continued helping out and then went home. I kept thinking about our conversation and I wanted it to have lasted longer, I would've loved another one, it was incredibly satisfying. I then realised that I wasn't becoming aroused and found him incredibly attractive too. Maybe I did before and not noticed but I certainly do now.

I haven't been able to stop thinking about him, speaking to him and a bit more. It's not realistic because he's much older than me and already has a partner but the way he looked at me and the way I felt during our conversation was beyond anything I've felt before. Even once other people finished talking to him he'd circle back to me constantly, it felt amazing because he showed such an interest in me. I felt like I was taking the conversation away from everyone else but he was incredibly easy to talk to and there was something about his eyes that have stuck with me.

I wish there could be more but I know it wouldn't happen. This is the first time I've ever felt so obsessed with someone, I'd give anything to just talk again because I could talk for hours with him it was that easy.

I feel really pathetic and a bit saddened by it because I've never felt so interested by anybody before.