I [23F] got ghosted after hooking up with a guy [24M] for the first time.

I [23F] have been seeing this guy [24M] we’ve been texting non stop all day every day across multiple platforms insta, tiktok, text, etc. we’ve been flirting and he reciprocates and seems very interested. (Calling me pet names, consistent communication, sending me things that makes him think of me etc) We’ve been going to a handful of outings where he’s been my date, and the last time we saw each other we hooked up. We both communicated we don’t want a relationship just fun dates and casual sx. He says he really enjoyed it and that he plans to see me and continue. But it’s been 3 weeks since then and he rejects all my invites to hang out saying he’s busy. He isn’t lying about his other plans he really does actually seem busy, but I also know when someone wants to see you they will. But if he isn’t into me why is he talking to me so consistently online and flirting so hard over text? He texts first, he initiates interactions not just replying to my messages.
Although I am looking for some casual fun I have communicated I value consistency and still want to feel respected in the arrangement. But it is feeling like he hit it and quit it after the first time having sx and I it’s causing me a lot of anxiety. I feel like there’s something I did wrong and I feel a bit used. I really enjoy hanging out with him and I would like to see him again but I also don’t want to be putting energy into someone who isn’t reciprocating the same. I need advice on how to handle this situation.