Why is he ignoring me?

So last Saturday (June 18) this guy who likes me and I like him back decided to text me. We text a lot. Anyway, we were texting until like 12 AM and then he just fell asleep. So on Tuesday, I just decided to say "Yo" at like 8 pm, but he never replied, but I didn't think much about it. Then, I decided to text him I think Thursday saying "Hii" at like 5 pm, but he didn't get it until 7 because my phone tells me when people receive messages. I'm not going to text him again without him texting me first. I just don't know why he isn't texting back because he likes me. His phone ISN'T broken.