Should I message him or just accept that he’s lost interest?

I (26F) went on two really great dates with a guy (26M) I met on a dating app. The first date lasted around 9 hours, the second was also great, and we ended up sleeping together.

He didn’t ghost me after sex. We continued texting for a few days, but I noticed a change. At first he’d usually reply within 2–4 hours, then it became 5+ hours, and one reply even took around 18 hours. His replies were still friendly and not dry, but he gradually stopped asking me questions or trying to keep the conversation going.

Eventually I sent a final message (“ahh lucky you”) that naturally ended the conversation because I wanted to see if he’d restart it or reach out on his own. He never did.

It’s now been 5 days since our last text. During that time he’s viewed my Instagram stories but hasn’t messaged me.

One thing that’s making this harder is that I don’t think he was lying when he said he was busy before. The reasons he gave were legitimate, and he even suggested we could try squeezing something in. I was actually the one who replied that we could just schedule something when we were both free, so I don’t think he was making excuses to avoid me.

Since then, though, I’ve decided not to ask him out again because I feel like I’ve already shown interest, and I’d like to see if he’ll make the effort this time.
Part of me wants to message him and ask if he’s still interested because the uncertainty is driving me crazy. The other part of me thinks that if he wanted to talk to me or see me, he would have reached out by now.

Would you send one last message for clarity, or would you take the silence as your answer and move on?