Tips on how to move on

I met this guy after i broke up with my ex. Maybe because I'm not used to the feeling of being single but I entertained him. It was fun talking to him and we even called a few times. He told me that he liked me but I didn't take it seriously because I know that he doesn't like me romantically. Long story short, we met up and slept together.

After that, he distanced himself to me. I couldn't helped but to noticed it. He told me that that's how we established the boundaries between us, and that we said that we're just friend. But I don't fuck with friends and the boundary has already been crossed?!

Anyways, I told him that I like him not because I want a relationship buy because I just want to put an end with this. He told me that he doesn't see himself in a relationship rn because of what happened to him right before we met. Anyways, it's fine. I already cut my connection with him.

But tell me! Why can't I just put this all behind. When I broke up with my ex bf for 2 years, I didn't feel sad at all. But rn, i can't stop thinking about this guy whom I only knew for like a month.

Can someone tell me what is this that I'm feeling rn? I know that he only like the idea of sleeping w me and after that, it's done. Maybe he already met someone new... How can it be so easy to him? Am I just too stupid?

I JUST WANT SOMEONE TO WAKE ME UP FROM THIS STUPIDITY