Am I being a paranoid idiot

If someone (i.e a guy, yknow not just a friend or family member but a romantic interest) said goodnight at 10:30 the night before but didn't reply until 5pm the next day? Cause he said he was sleeping. I don't want to think anything of it but this is someone who is one of those repliers that sends a message 0.1 second after receiving one. Am I overthinking or is this the sign I need to take that he's losing interest? This has just happened a few times before to me so idk what to think 😅