Online friend keeps wanting immediate replies and I can't seem to know how to feel about it

Context: There’s this guy I talk to online, and I recently realized he really likes me. He says he thinks about me a lot, and apparently, I’m a priority to him. At first, I thought he didn’t care, but now it’s obvious he does. (we're both minors)

The thing is, it’s starting to feel a little overwhelming? He wants me to reply almost instantly.. like within 1 min, and gets worried if I don’t respond within an hour.. he calls or spams my name just to get my attention. I like that he cares, and I like the attention, but I also feel stressed at the same time . What should I do? Or say?