Am I overthinking?

I have been talking to this guy for about 10 days now and he was replying really quickly for about the first 5 days. Even when I would reply slow he would open the Snapchat within minutes mostly. He’s a really nice guy and is kind. But for the past few days he’s been taking ages to reply most of the time over an hour, and I had noticed his snap score going up. I said to him yesterday if you ever lose interest would you tell me and he said yeah he would always tell me. We have planned to go on a date soon and he still talks about that. What’s going on. Am I overthinking or what’s happening?